Twitter is seven today. I think it deserves a cake. I'm on three major social networks: Google+, Facebook and Twitter.

Of the three, I use one of them rarely, one of them grudgingly and the other to the point of addiction. No prizes for guessing that the addictive one is Twitter.

Twitter is a mess, and I mean that as a compliment. My timeline is a mix of friends, colleagues, strangers I've stumbled across or who have stumbled across me and relatively few spammers and social media experts.

It's fast and frantic and occasionally irritating or even frightening, but it's never boring. This morning's crop includes lots of political stuff, a woman playing dead in a Glaswegian car park, some new short films and comics, a Girls Aloud playlist on Spotify, the weather in Edinburgh and somebody I don't know swearing like a docker, and that's just from the last 20-odd tweets.

For me, the highlights are many: messing around with colleagues during working hours, finding new music, sharing LOLs, discovering that legendary Scots musician @aidanjohnmoffat loves Girls Aloud as much as I do, following Ian Rankin @beathhigh as he worries whether his book in progress is any cop, or just laughing as everybody I know gets angry at #bbcqt or George Osborne's budget speech.

Twitter has become part of the fabric of our lives, so popular that Ed Milliband felt the need to make a painfully unfunny joke about it ("Hashtag Downgraded Chancellor," he said in the Commons yesterday. No, he really did). Meanwhile the Chancellor chose budget day to join Twitter himself, with hilarious results.

Twitter is great because you are

To its great credit, Twitter recognises that what makes Twitter special is its users - and so far it's resisted the temptation to Do A Facebook and ruin the entire experience. When I log into Facebook on my phone or iPad I get a full-screen ad for a Poker app, a bunch of crap I don't give a monkey's about and some carefully hidden updates from people I actually know.

When I open Twitter I get tweets. As the cliché goes, Facebook is where you connect with the people you used to know. Twitter is for the people you want to know.

That doesn't mean Twitter is blameless in every respect - its various API changes have messed third party developers around, it's a great facilitator for online witch hunts and it's a tremendous bullshit propagator too - but overall, it's still the anti-Facebook, despite Facebook's best efforts to copy it.

I think Michael Marshall Smith is right when he says that online relationships "can be based on unpredictable factors like whim, level of online drunkenness, or the cynical intent to build a following through empty follow-backs", but the beauty of Twitter is that if you don't like the results you can unfollow, or mute, or block such people, or hide them in lists - and those unpredictable factors can bring genuinely useful, interesting or amusing people into your life too.

Twitter reminds me of my first online adventures inside the walled gardens of CompuServe: getting to know all kinds of interesting people and occasionally getting into huge sweary fights with them. CompuServe made the world feel smaller, and Twitter does the same: it makes me feel more connected, more sociable, better informed and more entertained.

If Twitter could somehow serve beer, it might just be the world's best pub.