I have the opposite experience. I have no incentive to use new networks -- all my friends are on Facebook. Facebook is actually very good at (at least in my experience) showing me information from friends that I'm actively being friendly with. People from some event a few years ago fade out, while people I'm going to school with now are in full-swing. When I change my involvements during the summer, Facebook in turn fades them out and favors the other people I'm currently working with.

For me, Facebook does exactly what Kevin Rose desires.

I think his problem is that he, as he put it, friends people "in passing [he] hardly knows".