The most evident value of the social networks visibility at sites like Tribe.net seems to be trust - but trust has so many uses that one site has no possibility to explore them all. Instead SNSes could serve as [http://www.openid.net/ OpenID] servers for other sites. For example this could work for Carpool Network sites (like http://www.erideshare.com/), for http://Couchsurfing.com or for eBuy etc.