The Dunbar Number
If you’ve read The Tipping Point, then you’ve heard that the upper limit to human social networks is about 150 people. The name behind the number is Robin Dunbar, author of Grooming, Gossip, and the Evolution of Language. Razib discusses it in a recent GNXP post. The comments on that post led me to this Life with Alacrity post on the Dunbar number.