The Economist has an interesting little story about Dunbar’s Number, the theory that it’s difficult to maintain stable social relationships with more than ~150 people:

Primatologists call at least some of the things that happen on social networks “grooming“. In the wild, grooming is time-consuming and here computerisation certainly helps. But keeping track of who to groom—and why—demands quite a bit of mental computation. You need to remember who is allied with, hostile to, or lusts after whom, and act accordingly. Several years ago, therefore, Robin Dunbar, an anthropologist who now works at Oxford University, concluded that the cognitive power of the brain limits the size of the social network that an individual of any given species can develop.

I try (unsuccessfully) to keep to following fewer than 200 people on Twitter, but even that makes it tough to keep current. Following my ~1000 friends on Facebook is unpossible and I’ve given up.