I think Facebook is starting to become the de facto "people management" platform for individuals. If you like RSS it's basically turned into RSS for human beings, corporations, music artists, blogs, and so on. I think there is an incredible amount of data they have there on those groups and potentially stand to make a killing if they try to marry that with ad revenue. It beat Google for the most visited site last year somehow so it seems to be one of the stickier websites around that aren't related to search or email.