Rhodri Marsden: What can I do if someone is impersonating me online?

This is tempting fate, but no one has bothered pretending to be me on the internet. That's probably because there's nothing to be gained from doing so, other than receiving a few press releases about webcams and a truckload of spam. But as the use of social networks expands, any organisation or person in the public eye risks being impersonated; often badly, granted. And it's virtually impossible for them to take preventive measures. If you had it in for Kevin Keegan, there are so many websites where you could deploy a rich variety of Keegan-based usernames that a dedicated idiot could have a few dozen fake profiles online before the day was out.

The landgrab on Twitter began months ago. It's unlikely that Sainsbury has anything to do with twitter.com/sainsburys, or that Depeche Mode created twitter.com/ depechemode. But those are pretty benign examples; the person who dared to incur the wrath of ExxonMobil by pretending to be the oil corporation had his Twitter presence erased pretty swiftly, while a satirical 'Daily Mail' account was renamed "Not Daily Mail" by Twitter after similar intervention.

Meanwhile, thousands of people looking for celebrities on Twitter are finding it hard to work out who is real, so they turn to Jonathan Ross for help – because he seems strangely willing to phone up the celeb in question and just ask them, before posting his findings.

The policies of Twitter and Facebook are clear. Facebook won't let you impersonate anyone; Twitter won't let you impersonate anyone else unless it's a parody (although it's by no means guaranteed they'll get the joke).

What isn't funny is when people without any legal resources find themselves under fire. A distressed reader discovered herself on Facebook, and strongly suspects that her ex-boyfriend set up the profile. Her emails to privacy@facebook.com elicited no response – unsurprising, when a service has 150 million users and only a smattering of support staff.

Unless we fork out for a solicitor, we're dependent on the social networks giving a hoot about our little problem. So perhaps the best strategy is simply to avoid antagonising any creepy types who tend to hold grudges.

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Currently under discussion: Should I upgrade to Internet Explorer 8, or just abandon the good ship Microsoft?