Sources tell VentureBeat that Maestri's Mob Wars, a role-playing game for the Facebook platform, earns its creator $1 million a month off its 2,505,698 monthly active users, mostly by selling in-game player upgrades for real world cash. On top of that income, research firm DeveloperAnalytics says Mob Wars could make another $22,000 month selling ads because its users load the app's pages around 60 times a day.

Trouble is, Maestri developed and launched Mob Wars in January, before quit software developer Freewebs in February. After watching Maestri rake in the cash for months, Freewebs — now called Social Games Network — finally sued Maestri on August 11, alleging breach of contract, breach of duty, misappropriation of trade secrets and interference with business relations. Maestri told VentureBeat that "Mob Wars is my creation and the legal process is moving forward."

The list is topped by an widget called Mob Wars, which exhorts users to "Join the Mafia, and start your own mob. Band together with your friends to become the most powerful force in the elite criminal underworld of Facebook." DeveloperAnalytics says Mob Wars' users return to its page 60 times a day. Facebook's most popular application, Slide's FunWall, only shows up fifth on the list, because users load its pages just two or three times a day. Here's what DeveloperAnalytics didn't account for in running the numbers: Slide's opening an office in New York to sell its inventory to major brands, while Mob Wars ads ask if you want to take an IQ challenge.