Captain McGrandpa

Captain McGrandpa is an original game on Gametap that is designed to be a massively mutliplayer text based adventure game. The trick is that it's played through the Gametap forums using a specialized text parser. The game changes and the world evolves based on the players' actions. They essentially used the game designer as a sort of GM to react to the players' actions and write the whole thing, writing the code for the game I'm assuming, on the fly as it progressed.