The largest problem you have is that this sites new player traffic comes from people who play starcraft 2, and then play the mafia mod on it, and then follow to the website.

The solutions are:

1).Find a new game to create a mod on

Which, is difficult & unlikely to happen. (Perhaps the Command & Conquer game in development?)

2).Drag people in to play

This means, making friends in game and inviting them.
Getting active forum users to play forum mafia.
Bringing in people from elsewhere.
Put up a poster at your local community centre asking people to join the Mafia.




So yeh, Unless you get a group of people actively working to bring people into the forum mafia. Its going to remain as a small group of loyal individuals.

Only once you have a reasonable sized player base then its worth developing the site further. Unless someone wants to throw wads of cash at it.