Robert Scoble hits some good points about blogging relationship networks --
The truth is, my RSS News Aggregator is a far better "friends network" than Friendster or Orkut are. The problem is that it's hard to build a real friends network in blogs. Why? Cause you gotta do work. You've gotta read someone every day for a while. You've gotta blog and build up a relationship network. You've gotta link to them. You've gotta smooze with them at conferences and geek dinners. That's all hard.
But Friendster, Orkut, and Linked In, all promise a shortcut. "Get 100 friends without doing any work" they all seem to promise me. Hogwash. You want a relationship network? You gotta do it the hard way.
I've joined Orkut and LinkedIn and have build a moderate set of links with people I've worked with, but I've been underwhelmed so far. Other than the sign-up process and the quest to grow your network, there doesn't seem to be much going on in those groups. On the other hand, I'm reading blogs constantly, so perhaps that's where the relationship gold is going to be found.