Sorry, Ben, but you're not really my type.
Seriously, Friendster's model falls down because the networks are only really useful for one application, i.e., dating. Which means that people not interested in dating are less likely to join, and networks are a lot sparser and there are fewer people you can find through them. Tribe, however, has multiple uses (dating, organising events, selling stuff, discussion, &c.), which encourages more people to join and makes each application more useful in itself.
Is it connected to that whole Tribe dot-bomb thing? The one which was (supposed to be) sort of an inverted, hip version of citysearch for people who want to go to raves and have sex and stuff?
No; this is a San Francisco outfit; the other one was Australian.
San Francisco eh? Hmmm, watch out for the sort of 'friends' you might attract. Still, the Pope might be going to shut them down soon. Let us Pray.
So you weren't interested in a date then :-(