It was in many ways the signature social game, the one that defined what Facebook games were likely to be. It established the common parlance of levels and experience points among executives who'd never heard of D+D. But more than that, Mafia Wars was an unbelievable game.
It was a success that made no sense in the vein of how most of us thought of games. The idea that lots of people would engage in a game so apparently basic, and for so long, was incomprehensible. Love or hate it, Mafia Wars taught us something very important about the difference between how we think players play, versus how they actually play.