I don't know that I've ever done this, but has anyone ever Co-GM/DM'd. For example; A game world exists. There are a set of players in that world, but every so often, the GM/DM position is traded between two or more persons. Thus allowing everyone to be a player.

I'm just wondering how this worked out. I've never done it, though I have taken over worlds that haven't been used in a while just to mix the gaming up a bit, but they were never reused and continuity wasn't jacked up due to another GM stepping in.

Please, share your experiences with this idea, if you have any.