Seth Godin’s new book (Tribes) and accompanying social networking site explains more:
"One of the ideas I talk about briefly in the book is that powerful tribes aren't open to everyone. The exclusivity makes it work. .... Even with just a few people in the pre-beta tribe we've built, I can already see how powerful it can be to have a safe, well-lit place on line where like-minded people can connect."

‘Guidelines for the triiibe’ (or Tribes?) Seth Godin
• Everything on the triiibe, stays there. We agree not to cross post or to quote without permission.
• The best triiibe members are active posters in the forum and generous with advice and counsel. Lurkers... wake up!
• It's not a promotional platform. The goal is to learn and to help, not to sell.
• The site is by invitation only, and our moderators are free to disinvite anyone who's not making the site a powerful resource.
• It won't work without you. Thanks for joining.

"It's not a promotional platform. The goal is to learn and to help, not to sell."
I belong to an Elite (http://www.eliteleaders.co.uk/) Tribe (although I have never before thought of it as that). ‘Learning and listening without selling’ is alien to concept to many recruiters (on too many occasions myself included), but I suspect the most successful companies and company leaders over the next 18 months will belong to the Tribe mentality?
I would value your thoughts – tell me more – and I promise to listen.