Yes, I know what you are talking about. It was done here one time before, I think. It was a horror themed RP called Playground. Basically the OP built the story and the characters got to choose from multiple options of how the next scene could play out. Unfortunately it died out because there were way too many people the OP had to write for, and character interaction was almost non existent. So I guess you can take away a few ideas about what could go wrong with this type of RP and proceed accordingly. : )