CityVille recently introduced a new bandits system, revamping the police station and providing a new means to utilise your friends list. Perhaps a step toward more social asynchronous gameplay from Zynga? Perhaps not.
Facebook games do not succeed through compelling game play but being compulsive, using clever hooks to keep players coming back.
A solid Facebook game with some potential, however there are some balancing and UI issues that would require addressing for it to really take off.
CityVille is the most popular Facebook game out there. It is addictive and with some clever hooks, it drags you in… along with your friends!