There's an allegation that Conrad Black posted nasties on a Yahoo group about Hollinger under the name NSPECTOR, which, if true, is more than a little bizarre to anyone who's poiltically plugged in.
Here's a National Post piece about sock puppetry, Wikipedia and lawsuits for libel. The idea that people can trash people on the Internet and not be subject to the laws of libel (see p. 2) is ridiculous.
I was a party in a brief but nasty libel suit about an Internet posting, and I never took the position that the Internet is immune from libel litigation. In fact, Internet libels are world-wide and they are semi-permanent, since they're all cached.
As for Wikipedia being immune, forget it. In the States, Wikipedia argues that it can't be sued because it's a non-profit. That argument would make publications like the Salvation Army's Watchtower, Scientology's published material and the Walrus magazine immune. I suspect Wikipedia will eventually collapse in a wave of libel suits and threats of litigation. There are too many goofballs, people with grudges, folks with political points to make, and mischief-makers posting on Wikipedia.