I just started reading Dataclysm, the book by the guy from Okcupid. You can run your Facebook profile through the analysis. The closer the dots are, the more connected. It'll also pop out an assimiliation score: how important is that person to your network? Importance is determined roughly by how many people you would lose as second-line contacts if that person were to fall away from your network. This is mine:

That tight cluster in the top left is all my high school friends. Everyone has everyone as a friend. The bigger, but less dense cluster on the right are my current university friends. Bottom left are the few family members I have on Facebook.

I'd be interested in other people's networks. What does yours look like?