Well, rather than waffle on about it, here are some answers to the same question when asked by the Guardian.
@Aaron78: It helps me hoan my wrighting skillz.
@acton: Because it's the most addictive social game on the internet at the moment. And to share cool stuff.
@AdeBridgwater: For research and to gauge public perception of certain technologies before I write about them - and to vent spleen too.
@alisonhogarth: To keep in contact in a conversational manner with my friends that are far away. Also to meet new people.
@AsimQureshi: Twitter = RSS. All my favourite sources (be that the publication or the journos themselves) have a Twitter feed.
@ArenaFlowers: For communications with customers/visitors, for news (specialised, eg flowers or SEO or Forex, and general), plus sharing tidbits plus for fun.
@bbmorph: One (of several) ways I use Twitter is to communicate with people who might otherwise ignore me. As a community of 'early adopters', people who have joined Twitter for business reasons want to be seen to be in touch with the technology and the community. This makes it easier to talk to people further up the (imagined or otherwise) rungs of business hierarchy than one would otherwise be able to do. To analogise: it's not easy to walk up to the marketing director of a big company at an industry event and engage her in a meaningful conversation. If she's on Twitter, and you have something useful to show her, she's more likely to talk to you.
@BellaGrrl: It's a fast, fun and focussed way to share information. Plus it saves those around me from hearing what's in my head.
@benevetts: News/analyst feeds. Ideas of stories that media working on. Gossip - solo marketing/PR in-house can be lonely.
@biggreensheep: If Dave be "the home of witty banter" then Twitter has got to be the home of intelligent social networking. While other social networks rely heavily on gimmicks and apps, the Twitter platform holds community and content in high regard. Twitter's simple, no-nonsense approach makes communicating with like-minded tweeps and potential clients an enjoyable, and above all, worthwhile experience.
@bookmeister: For connecting with and getting info from new people who I know to have shared interests and values.
@BrockleyCentral: It complements blogging perfectly, allowing instant interaction with readers, from story suggestions to candid feedback.
@cambridgeunion: The Cambridge Union uses Twitter to keep our current members updated, to stay in touch with our old members, and to pester famous people.
@currybet: For finding out what you're having for lunch.
@Chris_Reed: To learn from, banter with, and sometimes help the most generous bunch of people that I'd previously never have met.
@childsi: We like chatting to people we might otherwise never have met or people who'd previously be on our wish list to meet.
@chuckdarw1n: I actually find it great fun. Mainly because I follow some very funny people and I'm only funny when I type.
@cwelton: To keep up with, and keep in touch with so many different yet notable communities. And to get noob advise!
@chattered: Because I like to keep my social networking friends close but my social networking enemies closer.
@danbraithwaite: To learn what the leading, and I guess not so leading, people in my field are reading/doing/thinking.
@davidcoxon: One beauty of Twitter is you choose who you follow - if they start to spam you stop following them.
@deekdeekster: I use Twitter because it keeps me touch with all the timezones.
@deekdeekster: I use Twitter because it satisfies my craving for twestions.
@deekdeekster: I use Twitter because my love for the people is boundless.
@DesignerBaby: I use Twitter to piss off my friends who still don't quite get what all the fuss is about.
@digitalmaverick: I use Twitter because it's broadened the range of people I can interact with instantly and I get authoritative responses.
@dirkp: Wer von Euch kann Ruby?
@DJ_Ringo: Networking with potential customers/clients.
@DJ_Ringo: And work avoidance.
@dogstrust: Because talking to supporters about what's important to them has to take place on their ground too.
@Dulafs: So I know what all the fuss is about. To spark ideas. And to not be too scared to embrace change.
@flashboy: The 140-character limit makes it the most efficient and streamlined form of procrastination I've found.
@fivesimplesteps: I use Twitter to market our recent eBook release and to interact and provide customer service to our buyers. It has proven to be hugely successful and a good example of people appreciating Twitter for business purposes provided there is a friendly human behind the brand responding to their questions and tweets.
@futurescape: To interact with friends, clients, managers, designers, authors and media personalities.
@gaseousbrain: It's the perfect social medium for accessing with a mobile device and it allows access to the most interesting people.
@griffwaunfach: I use Twitter because it's a great way to find news and discuss it with others.
@GPforhire: To rant about patients, de-stress and because it's the only social networking site not blocked by work.
@guyclapperton: Because I've had £1000s worth of commissions I otherwise wouldn't have picked up if I hadn't, and scored a book deal.
@handypearce: It harnesses the power of personal recommendation. And am easy way to know what's going on and find cool shit.
@hecklerspray: Because it marginally increases the likelihood of me kissing one of the failed X Factor girlband Hope on the lips.
@iabuk: Twitter is great for both gathering and disseminating information. We follow key industry commentators and use it as a news and comment aggregator. We're also able to quickly and succinctly communicate with our members, and as a commercial entity it's been great for driving ticket sales for our events. Now Twitter's considered to be safely in the mainstream, it will be interesting to see how brands will use it to further engage with consumers. As with all social media experimentation, some brands will achieve cult status while others will inevitably take their audiences (or followers) for granted by treating Twitter as just another way to disseminate the soundbites of their corporate communications department.
@jamesga: Brilliant online brand building tool and my preferred source of hot news and views on tech.
@jennylwilliams: 140 characters provides a unique platform for wordy delights and also the opportunity for honest networking.
@jennylwilliams: How else would I receive a good night wish from Stephen Fry?
@JosephHug: I work alone - tweeting gives me some much needed human interaction and is an intelligent sounding board for ideas.
@JoasiaK: It's a pretty good way of helping PRs to understand what's on a journalist's agenda.
@John_Muir: Why? Hive mind, buzzing in my ear.
@JonClements: To create this heightened, technological mystique among colleagues that what I do all day is unfathomable.
@joshhalljourno: Twitter is one part of expanding/deepening my knowledge. Only follow people who I can learn from, see what they're reading. Engage.
@juliansaunders: There is news, there is insight, there is opinion, and then there is Twitter. It's my feed to the second by second pulse of life.
@kajutan: Because it's like standing on a plaza and listening to people – you never know what you will hear.
@katebevan: Work avoidance. Obviously.
@katemoross: I use Twitter: when I have something to say, that isn't important enough to blog, or call someone about, but I still need to get it out my brain bubble; when I want to share an idea, a question, an image that is fleeting, that is somewhat ephemeral; when I want find something out quickly when I am on the move; when I need help from a tech head; when I want to update people on a product or service under my brand or company; when I have sales in my shop, giving people promo codes to get Twitcounts; and because I just don't have time to interact with larger online portals, I just want instant direct contact in two clicks.
@larakiara: To share my dull, banal musings with dull, banal people. People don't actually use it seriously do they??
@Laurajohnson: To learn what's going on in a snapshot.
@lauraroth: To make new contacts in the industry that I work in and to find out the latest news - also great for sourcing speakers.
@lukeregan: For conversation, to share and absorb knowledge, to crowdsource questions, for networking and for research.
@manchesterisace: After discussion with @megancodling t'other week we came to conclusion we love Twitter because we are very nosey.
@MarkABaker: Because it helps me communicate with my personal and business network and stay on top of current events.
@mattchedit: We use Twitter in a similar way to blogging - it's just faster and more reactive!
@matthewgain: I use Twitter because I get quicker responses from people than using email.
@MonaWalsh: Because Terry Wogan doesn't get it but mentions it loads on his radio show - oops, did I just admit I listen to Tech Weekly?
@mseasons: Because I really, really, really hate using the phone.
@neilp: I use Twitter because I can't be bothered with Facebloat and I can't invest the time in a decent blog.
@nijay: Because it's so unexpectedly useful. I keep in contact with people, get insight into people's personalities, and share information.
@Old_reprobate: Sad git's only contact with the outside world.
@oliverspall: I use it to talk and listen to peers, friends, enemies and people who make me laugh. It's also very good for ranting.
@patroclus: I get to hear the news before it's in the papers and I get to watch the cut and thrust of intellectual debate.
@paulraeburn: To pick out the gems from the rivers of mediocrity.
@PeterBale: Twitter is an effective way of communicating on issues a that would otherwise become time-consuming 600-word blogs.
@philcampbell: Twitter allows me to converse to a large density of people from a variety of background and places rapidly.
@photo_ed: To stalk celebrities of course. Duh!
@priyalI: I began using Twitter because my constant Facebook status updates was laughed on really. I realised I need a tool to share my thought/information and other activity 24/7. Also I don't meet new people on Facebook - I just make contact with acquaintances or old friends. I am from Mumbai and Twitter was my first source of information on the attacks - being in London there was no coverage on it for the first one hour of the attack. Now I meet journalists, bloggers, classmates and whole new set of interesting people via Twitter. Since I am studying journalism myself (MA in international journalism at City University), it's a brilliant networking tool. I also know who Stephen Fry is...
@psigrist: Because - and I didn't see this one coming - it appears to have revved up my social life. (The offline one.)
@PurpleLotus9: To arse about? And play 'confectionary wars' with my niece back in England.. What? It's serious stuff!
@rhysllwyd: I use Twitter because it's not Facebook.
@robwatts: Lots of reasons one being because my journey to and from work would be as boring as hell without it!
@rupinjapan: To get my news before I need to open a paper. And no bloody adverts.
@SamJaneMorris: 1) I always know when my team are going to be late and why 2) can eavesdrop on events I don't get time to attend.
@scottmalthouse: As a journalism student I use Twitter for contacts, as well as a way to get my blog posts read by more than two people.
@Screenjabber: For building useful contacts and getting information to help me in my work. And for fun, of course. Because it is.
@sjkennedy: I use Twitter to stay abreast of the really important topics in the tech blogosphere. Much more effective than RSS.
@snorestore: I use Twitter to relieve the boredom of daily life. It's the best excuse yet not to do any work.
@SophieGray: I'm very new to Twitter but I've found it's a great way to network and build up relationships with key contacts. It's a novel and exciting way of getting answers to questions and sharing information. Basically it's the new way to communicate in the digital age - quick and simple. What could be easier?
@technicalfault: To read Tweets from you.
@the28wall: To stay abreast of Charles Arthur's dislike for those working in the PR industry.
@tombot18: Because I like to feel like people care what I'm up to.
@Torgwen: It's good for my health. Quick access worldwide to huge variety of people. I read many more articles on websites, feel motivated by others' tweets and love the juxtaposition of my friend's tweet about breakfast with Stephen Fry's in the US.
@trendsy: Is now a trending topic on Twitter.
@tweehee: I'm using Twitter to bring together new comedy writing and raise cash for comic relief, it's a great way to have a laugh.
@tweetyourstreet: I think simplicity is the reason I use Twitter rather than blogging to communicate. I'm lazy.
@twishes: We like chatting to people we might otherwise never have met or people who'd previously be on our wishlist to meet.
@virtualewit: Networking, socialising, asking responding to questions, keeping in touch and keeping up to date.
@wearelondon: We use it to keep some clients up to date on what's happening, learn the same from others, spot trends in media, marketing and social communication. We have also started tracking a lot of customer feedback about client websites, we are a usability company, and are starting to engage with these unhappy customers to find out what exactly went wrong with their visit. In the future we may well use this as a real time usability insight service and build up panels of active customers who we can track online through their Twitter status.
@wolfeeboy: What are 'twestions'?
@wonkydonky: It may seem obvious, but as a normal user I just find it a fun and engaging way to find out what friends and contacts are up to, and hear what influential people are watching, talking about, thinking and the like. However, as a PR I use it to chat to media contacts both journalists and other PRs, but in the case of the former, it's incredibly useful to see what influential journalists are writing about, thinking about and talking about in the industry. It both improves one's knowledge of the industry issues and markets, but also has the potential to lead to pitching a client if someone is writing about something an area relevant to my portfolio of clients.
@yiannopoulos: Cos there ain't no-one fitter than the lasses on Twitter.