In my teens I was an active member of photo.net. Back then I registered with my real name, not really considering the long-term implications. Several years later, I find that no matter what I do, the website won't change, hide or remove my name. I don't like the idea that when someone searches for my name, photo.net is always near the top of the results. Chris
A few sites will change a name on request, but once something is posted on the web, it is practically impossible to remove it. Even if a site took the trouble to remove your comments, they could well survive in various search engine caches, mirror sites, Usenet messages and the internet archive known as the Wayback Machine (http://www.archive.org/). In the longer term, however, many sites go bust and vast amounts of new information swamp the old stuff, so earlier posts should become progressively harder to find.
I do have some sympathy for Photo.net, which told you that its use of real names tended to improve the quality of the discussion: "We don't aspire to be an anonymous mud-slinging forum." The Guardian's website provides ample confirmation of John Gabriel's theory that given anonymity and an audience, even normal people tend to behave like jerks.