I'd say a primarily community of interest. The Burn Tribes I'm a member of (especially the one I moderate) are very active- I haven't been to the main Burning Man one in over a year (and 100,000 new posts) because it's TOO active, largely with trolling and flaming. OK, maybe not largely, but people sure weren't treating each other nicely!!

I think it really takes a few factors- a core of high-participation individuals, a generally genial feel, a community of interest and a unifying purpose people can sink their teeth into and have passion for- all seem vital to the continued health and growth of a Tribe. And I don't think any of these factors is dispensable- ESPECIALLY having a core of active members.

Because really, when it comes down to it, the reason Myspace can never be as amazing as Tribe is CONTENT. We're interacting here- I meet new folks all the time and while the photography and art really knocks my socks off, it's the writing I come back for. Nothing against Myspace, which has its role, but I've rarely been inspired there, been moved, or begun an important relationship.

That said, as much as I love Tribe, contribute frequently, and want it to stay around forever, logic tells me that everything eventually runs its course. I suspect a Tribe about a TV show fades after the show goes off the air, if not completely, then largely, becoming something different if it survives at all. I'd be interested to see the numbers re: average Tribe life-expectancies- not based on existence (I know there are tons of Tribes no one has used in years and just not bothered to delete yet) but on usage. Anyway, interesting topic- thanks!!

Tribingly and Participatingly,
Major Tom