I wonder how they are generating value? The funny thing is that it appears the group based social network idea is in the air right now, and there was even a post on HN by someone trying to make something rather similar (see: http://news.ycombinator.com/item?id=1579400 ). Unless they move in first and fast this space will get really crowded.

They could make something that exploits their social graph, kinda like Aardvark, but that again is something really long term. So, what is their value proposition in making users join right now?