Linkedin seems to be basically gathering marketing data so people can bother you. Then you end up with people wanting you to create testimonials were they ought to be none.
Facebook has revoked much of its privacy features and that has turned me right off it. It was the king of networking for me, but this has totally ruined that now.
Myspace is too gimmicky and bloated. Bebo dying as most the people I know dont even use it anymore. meetyourmessenger seems to be a way for weirdo's to get your data.
tagged is boring and not user friendly. Friendster is a clone of Myspace and less popular.
The only thing about twitter I like, is its quick to use, but its not powerful in the sense of the others.
So this new Buzz from Google seems like another Twitter, at least I already log into Google for most things each day, so its one less thing to put a password into.