The big news in Facebook games this weekend is just how fast Zynga’s CityVille is growing. As of this morning, CityVille has grown to 22 million monthly active users (MAUs) and over 7 million daily active users) making it the second largest city in the world.

Why is CityVille growing so fast when virality is dead on Facebook as pundits (such as myself) like to say?

Aside for the fact that it’s a very good game, Chris Morrison of Inside Social Games lists 4 reasons for the success of the game so far:

  1. Cross promotion: Zynga is promoting CityVille like crazy on the bar atop of it’s other popular games as well as co-promotion within its juggernaut hit FarmVille. When you have 250 million gamers you can co-promote you, you have an advantage of every small game developer out there. Of course, this strategy works if Zynga players continue to play CityVille and their other games. If you are just robbing FarmVille to feed CityVille, what’s the point (someone with more time than myself and a better inclination for numbers should run the analysis and ping me).
  2. Localization: Zynga launched the game in 6 different languages and international growth is definitely fueling the game. Curiously, Zynga picked 6 European languages to release the game in when it was obvious that a game about urban planning and growing skyscrapers would be an obvious hit in the fast-growing Asian countries of the Philippines, Malaysia, and Indonesia. Inside Social Games estimates that only a quarter of the game players in CityVille are American. A reason why Zynga ignored non-European languages at launch is that though growth in social games is coming from Asia, those countries are notoriously more difficult to monetize (meaning, players less likely to pay to play) then in Europe. There are also a lot more languages and dialects to translate to in that region of the world.
  3. It’s a good game: The joke among game reviewers for social games is that game developers don’t launch a game in beta when they launch on Facebook; they launch it in alpha. This was not the case with this game which as I mentioned in my CityVille preview, was more polished and a deeper game at launch than most games we review that have been out a year. Most game companies can’t get rid of all the bugs before launch because they don’t the luxury of time or internal scale to test before launch. With 1300 employees and a zillion dollars in the bank, Zynga has that luxury.
  4. Working the system (Inside Social Games’ words, I must cite and that I like). Though Facebook frowns on game companies designing games around its communication channels, Zynga continues to push it to the limit. They are not breaking any of Facebook’s rules because they would not risk being banned by Facebook, but they are not being shy about asking you to invite and share with your friends on Facebook in every possible way. When Zynga is not trying to get you to spread the game through your Facebook friends, they are communicating with you through Zynga mail every … possible … moment.

When you combine all the ways you can communicate with friends to move up in the game through Facebook and through Zynga mail and their toolbar, it is fair to say that Zynga is pushing virality more with CityVille regardless of what Facebook’s policies are. And with 20 million users so far in the game, there is nothing Facebook can do about it. Seriously, what are they doing to, take down CityVille and make 20 million Facebook users angry? No way.

Does that mean CityVille is a success? Indeed it is, but with great fanfare comes great expectations. True, CityVille is the fastest growing game for Zynga. But there was no doubt in anyone’s mind that the game would not be as successful as FrontierVille with 20 million MAUs. The questions remain: Will CityVille be as successful as FarmVille (60 million MAUs)? Will it be successful on the iPhone and iPad when it launches later on those devices? If the answer is no to either of those questions, CityVille will still be a success but not as big of one as Zynga hoped.