360 was not designed to be YASNS (Yet Another Social Networking Service). The goal is not to amass as many "friends" as possible, unlike Friendster, Orkut, and others. It's about making it easier to share stuff with people who really are you friends--tne ones you already talk to, email, IM, etc.
Jeremy also has links to several articles about the new service and has some thoughts on ETech... Yahoo! 360 is currently by invitation only, but is expected to go live on March 29...