A good analysis from Cory Doctorow:
Imagine how creepy it would be to wander into a co-worker's cubicle and discover the wall covered with tiny photos of everyone in the office, ranked by "friend" and "foe," with the top eight friends elevated to a small shrine decorated with Post-It roses and hearts. And yet, there's an undeniable attraction to corralling all your friends and friendly acquaintances, charting them and their relationship to you. Maybe it's evolutionary, some quirk of the neocortex dating from our evolution into social animals who gained advantage by dividing up the work of survival but acquired the tricky job of watching all the other monkeys so as to be sure that everyone was pulling their weight and not napping in the treetops instead of watching for predators, emerging only to eat the fruit the rest of us have foraged.
