WHICHEVER decade your teenage years belong to, there are certain key themes that remain constant. Namely, and in no particular order: Zits. The opposite sex. Exams. Parents who don’t understand you. More zits. Oh, and doing and saying things that are so monumentally ill-judged, they’re enough to have you cringing into pensionable age.

Of course, some of us never quite shake the latter quality entirely – but there’s no doubt that when you’re 15, your capacity for buffoonery is magnified to a breath-taking degree.

Nevertheless, there’s a crucial difference between today’s teenagers and those of us now in our thirties, who experienced that era in the glorious late eighties and early nineties. There’s little record of what we got up to.

There was – and remains – little or no evidence of those puffa jackets, the experimental hair dyes, the cack-handed attempts to recreate Madonna’s Vogue, the dubious cocktails at somebody’s party, the window that was consequently broken and the pyrotechnical illness you suffered the morning after.

All of these things – which are, obviously, purely theoretical examples to illustrate the point (ahem) – are consigned to your own and your friends’ memories, to be reignited only during school reunions.

Not so the poor souls in their teens today. Because today, there is Facebook. Addictive, brilliant, ubiquitous and in the wrong hands – which fifteen year olds’ undoubtedly are – dangerous.

Ask Eric Schmidt, the chief executive of Google, who warned this week that young people are exposing so much private information on social networking sites that they might have to change their identities in future to get a job.