The one thing that jumps out at me when thinking about those older network is friends-of-friends... I have cool friends, and my cool friends have cool friends.

The one thing that jumps out at me when thinking about those older network is friends-of-friends... I have cool friends, and my cool friends have cool friends. So I'd wind up friending people on whatever network because I liked how they interacted with my friends. But yeah, common-interest groups are way better than the de-anonymized social graph of Facebook.