CityVille is now the most popular app ever on Facebook, with 84.2 million users. It even beats FarmVille, both in total users and in its ability to make money for evil Facebook gaming empire Zynga.

This sort of popularity is what we worried about when Zynga launched CityVille less than three months ago. CityVille has rocketed to popularity in less than three months through cross promotion on Zynga's other smash hit, FarmVille, and by offering gamers such enticing rewards as "pellets," i.e. shiny imaginary inducements like digital stars, coins, and "energy bolts." People pay very real money for these virtual items; indeed Zynga is said to design its games not to be fun but to induce a "compulsion loop" that makes addicted gamers shell out hundreds of dollars at a time for in-game products sold by the company.

CityVille is no exception. VentureBeat's Dean Takahashi writes that "every move you make... takes energy, and your stores need inventory to sell. Both are in short supply. If you want to... generate more inventory and energy, you can purchase it with real money." Unless 84 million people made it their New Year's resolution to spend their money more wisely, Zynga should have a great 2011.