We wrestled with the structure issue - giving people the freedom to build takes away the ease of conveying what it is. As far as gaming the system, we envision 3 levels of proof: honor system if it's a game between you and your friends, photos and video as the next layer up, and ultimately assigning "superplayers" to referee and approve certain tasks. Revenue model one of: let people charge to play the games they create, let people resell virtual items or currency, or allow commercially sponsored games.