So, when I was young and D&D was new to me, we always wanted to play and DM so we did.  We drew up a map, each of us drawing a quarter of it, rolled up a couple characters and took turns DMing each other in the same session.

But with all this troupe style play and rotating GMs from scene to scene and narrative stuff I wonder what it would look like if everyone was in the same party and DMing each other at the same time?  I'm envisioning something in a more board game style but with player directed control.  So if the party's in the dungeon I drew up I get to DM it but have limited ability to do various things, say make choices, search and find treasure, must take last pick of the loot.

I don't know exactly, I've never tried it, has anyone else?

Long, long ago, when I was in my teens, I did something like this with another GM, where he had half the game world and I had the other half.  But we crazily did it that if anything happened in "their" side of the world, that person was the GM of it.  It didn't really end up working well, I seem to recall.

Rune and Rocket Patrol both have rotating GM rules but yeah, I'm thinking you'd need pretty mature and balanced players.

I knew two guys who ran a campaign together. I think one generally handled most of the NPCs while the other GM managed the other GM duties (but it was a long time ago so not 100% certain on that). It seemed to work well for them, particularly because they had two people rather than one to prep before sessions.

I think partly what I'm thinking about would be an aggressive, competitive play style rather than a cooperative one.  I think encounter building rules would be pretty key.

Actually, that gets me wondering if Rune was a major influence on 4e.