AirBnB facebook fanbase is one of the fastest growth right now. The site went from 42,000 fans in end of June 2011 to 75,000 fans in beginning October 2011.
That's a 80% Facebook fanbase growth in 3 months.
How does it compare to TripAdvisor...
AirBnB doubles its Facebook fanbase in 3 months | Heykuki News