Big congratulations to the CrowdStar team on the successfully launch of Happy Pets, yet another great social game on Facebook. In just a week Happy Pets went from 0 to 890,000 Monthly active users. Amazing. Following Happy Aquarium's tremendous success not long ago, this is just shows that it wasn't a one off only. Keep a close eye on these guys - they are going to go far. Social gaming have just started to take off, and it is definitely not the-winner-takes-it-all market. There is plenty of room for new companies in this space. The key thing for all social games though, is to convert active users to active paying users. My advice: focus on optimizing mobile payments to a more salient place in the UI.
Disclaimer: I sit on CrowdStar's advisory board.