I'm still working on my own RPG, and it recently came to me that I'm getting kind of tired of being the perpetual GM, and especially in a story-focused group game (in a modern setting) there's a lot of potential to be tapped in drawing out the creative concepts from all the players, not just one person's crafted story. (In part, this is emblematic of the 'My Chicago' concept from the Dresden Files RPG. I'd like to se it taken further, though.)
I was hoping you guys would have examples of various GMless systems, and not just a list (since there are lists to be found easily via searches), but also your opinions about the implementations, including their success and failures. I'd curious to find out what kind of range the concept has, since it seems very much like new territory in gaming.
My own thoughts tend toward dice-based randomized simulationist methods, using rolled tables for effects, and dice-based AI for NPCs. Alternately, my other train of thought is to break the game into competing empires, with each player taking a strategy-game-style control of a portion of the game world, basically turning any one player into a GM based on what topic, faction, or challenge they face. (I've got a few other vague concepts, but I'm curious to see what already exists.)
So, how about it?