Social game powerhouse Zynga officially debuted its rewards program for all games on its platform today, allowing users to earn credits that can be spent on virtual goods.
Called RewardVille (sticking with the naming convention behind such hits as CityVille and FarmVille), the platform lets players earn zCoins and zPoints for playing the company's various games. The more users play, the more they earn. The zCoins can them be redeemed in RewardsVille for exclusive items that can be applied to any Zynga game. So users could earn the points playing FrontierVille but spend them in Mafia Wars.
Earning more zPoints unlocks new types of virtual content to buy. The whole program is designed to encourage users to play more games longer.
Virtual goods have become a big business. Snoop Dogg, for instance, earned $200,000 selling branded virtual goods  like t-shirts and jewelry in games like WeeWorld, Gaia Online, Zwinky and others. Dr. Dre in December partnered with Zynga  to provide branded headphones, weapons and cars in Mafia Wars, in which he also allowed users to stream his new single "Kush."
Collectively, Zynga's games attract 200 million users.