Apart from the International version, the Dutch, Turkish and Portuguese versions are the biggest versions.
Already more than 3.5 MILLION people have played Gangster Mafia Game!
Mafia City players like to spend time chatting with their friends on Mafia City's own IRC server. There are typically 4000 people or more logged into this.
Mafia City boasts typically more than 70,000 players logging in every day to chat, race cars and kill each other, all in the name of fun!
How To Measure Mafia Games Success
PopCap's VP of social operations on why MAUs may not tell the whole story

The mafia game buzz, focused largely around the Facebook platform, has become something of a roar over the past 18 months. Debate rages on a range of subjects from how companies make money to game quality (are mafia games 'real' games?) to the futurespective of how the social space will evolve.
One of the most frequently asked questions is 'who will be the winner(s) in the mafia game space?' Is it as simple as looking at the plethora of data on the Facebook social game tracking sites and identifying who has the most daily or monthly players? We suggest there is more to it than that.
People often talk about the mafia games space as if there will only be one 'winner' but clearly the space is broad and deep enough to support multiple successes. How winners achieve their long-term success on social networks is still to be decided but what is clear today is that there won't be a single style of City Mafia game that 'wins' the platform – social audiences are too vast and divergent in their needs and expectations to be satisfied by one game that meets everyone's expectations. Here I share some of the thinking behind how PopCap approaches the social space.