CrowdStar and Facebook have announced a five-year deal where Facebook Credits will be the exclusive in-game virtual currency for current and future CrowdStar games.

Interestingly, CrowdStar shared data on how well Facebook Credits are working for its existing games. According to CrowdStar, since adding Facebook Credits in December 2009, revenue per customer has increased 50%. Though there were probably other factors as well (improved monetization techniques, more mature users), Facebook Credits appears to be a factor in terms of increasing the trust factor. In return for being a test partner, CrowdStar has benefited with extra promotion from Facebook, helping it grow its latest game, Hello City, to 5 million players.

This is all a moot point, of course. One day is the future, Facebook will require all game developers to use Facebook Credits in return for being on it distribution platform and taking advantage of its social graph.

With the negative press from some game companies that Facebook Credits have hurt their business, this announcement surely helps Facebook’s case for Credits and cements CrowdStar as a leading social game developer in the future.