I think they can build a lot of ways in which the "community" angle adds value to a guest.

For example, they could encourage hosts to provide a list of top 3 things to do / eat / see, and aggregate this for guests.

Based on a guest's FB profile, they could suggest neighborhoods where they would enjoy staying, or connect guests to hosts who share similar interests.

There is so much potential, and I won't hold the current lack of community oriented benefits against them. Startups put a stake in the ground, and then build towards it.