Marc Canter sent around a draft UI for a social networking service for Greatful Dead fanatics. I actively don't care, and that's what's so great about it.
Most online social networks have the life of mayflies, because they are shallow. People gather in groups, post their favorite icons, chit-chat a bit, and move on.
By contrast, the Dead service is deep. The service lets Deadheads relive their roadtrips, using the database of recorded shows on-line at the Internet archives. Members can create a personal timeline of shows, and reconnect with people they met in parking lots and muddy fields.
This timeline would be locked to the DeadBase timeline (both music and event-ology) – so folks would indicate which shows they attended and use that to find DeadHead friends. Memories, finders, mementoes, salutations, etc. could all be left on a public bulletin board. But most importantly old friends could be reunited.
Activities that really engage their participants can be deadly dull to outsiders. But that level of engagement is a sign that community is lively for insiders.
Shallow YASNS are fads. How often have you visited Orkut or Friendster lately? A deep networking service, supporting the particular interests of the community, has the potential to stay and grow.