So universities and employers are checking the internet to get the dirt on us all, are they? Well, it's unfair: just because someone's image is on a site doesn't mean they were asked: "Would you mind awfully, old girl, if I put that picture of you wearing only shaving foam and a grin on my Facebook page?"
OK, if you stick your own embarrassing photo up, perhaps you're fair game. But that's not always how it happens. I went to a school concert recently one of those elegant affairs with Pimms, Purcell and Politeness only to find afterwards that one boy's (brilliant) performance had been filmed and put on YouTube. And there was I, in a front-row seat, my hair sticking up like a porcupine the way it does once the John Frieda mousse has worn off.
It wasn't incriminating: I was behaving myself, even if my hair wasn't. But I could have been scratching my armpit (or much worse), and that would have gone down a storm with my sixth-formers. One silly mistake and you're marked for life. Ask the Home Secretary.
More alarming was what happened last year. On leaving day, my Year 11 form persuaded me to sing. I had been criticising their out-of-tune impersonations of Franz Ferdinand for ages and it was payback time. I gave in. (Call me foolish, but pre-internet you could be foolish without being famous and no one cared.) Anyway, I'd belted out three lines of "You are My Sunshine", opening my mouth nice and wide like they told me at infant school, when I realised that several pseudo-paparazzi had their mobile phones out and were filming me. Line four of the song became, "When skies are... put those damn things away." It was breaktime afterwards, but I made them stay behind and delete the images that would have appeared on YouTube, entitled "See my Gullible Teacher's Mucous Membranes".
Have you tried tapping "teacher" into the YouTube search box? It's not pretty. Correction: some of the teachers on the clips are pretty, but the reasons they've been filmed usually aren't.
I'm not saying it's always malicious. That's the problem. Most teenagers see it as nothing to get bovvered about. One boy told me it was normal to take pictures of friends drunk, snogging or semi-clothed (or all three), and equally normal for no one to mind if the pictures appear on a website. They don't think about the fact that one day they might be a celebrity, a government minister or even, if not the first two, a moral leader. In 10 years' time, the hacks at the Daily Gossip would have a field-day with them.
It's wrong for anyone to trawl the internet for potentially damaging material. Teachers and other adults don't always give permission. Children don't always realise the danger. Both are vulnerable. I still check YouTube regularly in case one of those Year 11s slipped my notice. My future employers, take note: I learned my lesson.
Fran Hill teaches at an independent school in London