When Facebook turned five, we - OK, I - said its success wouldn't last.

That may have been premature. Facebook is six today, and it's still piling on the users: last year it had 150 million active users, and now it's got 350 million - 200 million of whom appear to be spamming us with invites for Mafia Wars.

So were we wrong, or is Facebook just taking longer to jump the shark than we predicted?

It certainly looks like the former. The continuing rise of Facebook demonstrates something pretty amazing: the way in which technology is becoming increasingly available, affordable and egalitarian.

People we'd never have expected to see online in a million years are now online, and more often than not Facebook is the thing that's got their attention.

So, Facebook is brilliant, I'm a great big numpty and everything in social networking land is groovy.

Not so fast.

Facebook isn't popular because it's good. It's popular because it's popular.

Facebook is the budget airline of tech. If Margaret Thatcher were to start a company that ran around giving small children Chinese burns, blasting Jedward through your windows at 3am and interrupting your thoughts every fifteen seconds with the wit and wisdom of Katie Price, it'd still be more popular and more loved than budget airlines. And yet millions of people fly with them every year.

Why do they do it? There are two kinds of passenger: passengers new to the airline, and passengers who've flown with them before. The former are excited, their brains full of the possibilities.

Grin and bear it

The latter grin and bear it in the knowledge that it's the only way to get where they want to go at the price they want to pay. If they don't, no problem: the airline just does a few more rubbish ads to attract some new passengers.

Facebook's rather like that. To its constant stream of new arrivals it's a playground, a world of joy and adventure. They haven't been on long enough to get sick of the oversharers and quiz takers - in fact, the odds are that they'll be the oversharers and quiz takers - and they weren't on Facebook when the various privacy controversies took place.

They're far too busy playing FarmVille to worry about the enormous amounts of information a remote and unaccountable corporation is collating about them.

To the old hands, it's a compromise: they're not keen on the privacy implications, on the way in which the Live Feed/News Feed distinction buries everything important and ensures you see only trivia, and they'd rather not spend half of their time fending off invitations to play stupid games, take part in stupid quizzes, or become fans of stupid products - but that's where everyone else happens to be.

Of course, not everyone grins and bears it. Some commit Facebook suicide; far more simply stop logging in.

But Facebook doesn't care, because every new sign-up invites all their friends, who invite all their friends, who inviteā€¦ eventually Facebook will do something really, spectacularly stupid, or everybody will hit their 150-friend mental maximum, or The Kids will realise that Facebook's becoming OldPeopleBook and will head for a service their parents can't use to annoy them.

For now, though, Facebook is flying high. See you next year!

-------------------------------------------------------------------------------------------------------

Liked this? Then check out Top 15 things you should never do on Facebook

Sign up for TechRadar's free Weird Week in Tech newsletter
Get the oddest tech stories of the week, plus the most popular news and reviews delivered straight to your inbox. Sign up at http://www.techradar.com/register

Follow TechRadar on Twitter