I think its just a matter of time. Airbnb is working on establishing itself as a major player in the travel industry, and they're not quite at the luxury villa stage yet. I imagine it takes a lot to win over the demographic who can afford these places, but you gotta start somewhere, right?
Even if there were reviews, it's impossible to discern astroturfing from legit information. National and international hotel chains do not have this problem.
http://www.airbnb.com/rooms/20478 (0 reviews, N/A response rate) http://www.airbnb.com/rooms/62627 (0 reviews, N/A response rate) http://www.airbnb.com/rooms/21031 (apparently the only customer has been AirBnb itself) http://www.airbnb.com/rooms/55179 (0 reviews, N/A response rate)