According to an admin on the game's official forums (as reported by Joystiq), there is a glitch in Gotham City Imposters that resets earned stats and unlocked content. The thread already has 63 pages of angry Gotham City Imposters owners complaining at length about the problem. When the core of your game is "online multiplayer" and the goal is to build an online record of your exploits, you can understand why players might be frustrated. Customers who bought XP bonuses and other baubles to give them an edge in leveling up are particularly agitated with the wipe.
Another official forum post is suggesting that the error is occurring for those gamers who have bought the game by converting the trial version to the full version.
We'll have more on this story as it develops.