Why doesn't YC make a Hackerbook (HB) to facilitate nerd networking? I read HN cuz I can't stand digg et al. I might use HB cuz I can't stand FaceClutter...uh...Book.
What features do users want?
Beyond that, why not just let the users define their own boxes? Though I'm not really sure what multiple boxes can do that one box can't.
Business networking site XING also has user's list what they are currently looking for and offering