I've had experience with a non GM led RP that was incredibly successful. On my old forum, a user started up an rp that only ever involved the first post, and after that they vanished. But the rest of the players, of which there was about 6-8, simply carried on and used the setting that was available to detail their characters coming together and interacting, and together we would add and contribute things and build off each others' works and in the end we built up a pretty nice and vibrant rp that was successful. The original rp creator actually appeared much later and was stunned by the success and dedication of us players, and was quite bewildered by it. :lol It was a fun experience. 

However, the reason why it worked is because the RPing community I was a part of was pretty small, and most of the players there were familiar/recognisable to each other, even if we hadn't rped with each other before. And everyone there was, like I mentioned before, communicative, dedicated and willing to listen to advice and constructive criticism from each other in order to become better rpers. We all grew immensely, and in that situation, well... we really didn't need a GM. But that's because we were like minded rpers all with a similar rping skill level on a small and dedicated fanbase forum. 

On a forum with a community as large and diverse (even within all of its various subcategories, there's a massive spectrum of 'skill' within Free, Casual and Advanced) as RPG, I don't think this kind of thing would work. And also partly because of how flaky a lot of players can be who end up needing to depend on a GM to guide and lead them. I think a GM less RP could work on this forum, but it'd be incredibly rare and unlikely, and a GM ran RP has a much better chance of success. That said, the % of successful rps is incredibly low anyway, so...

[quote=Magic]Personally I find there are two main advantages to a lack of a GM.1. More overall creativity. You have multiple minds going 100% out in creating a plot/story, not one mind with the suggestions of others. Assuming they're mature enough to allow their creativity to co-exist and not override one another's creations it can make the world that much more expansive and meaningful for all the players. [/quote]

[quote=Brovo]I'm sorry, but... What? How is a person's creativity lessened by having a GM? That doesn't make any sense. In fact, all having a GM here would do is help ensure that the world makes coherent sense as one person ultimately decides what does and does not fit, instead of a few or even several minds all simultaneously adding to the world and each potentially causing errors to one another's works ranging from chronological to physical to scientific and so on.

In my experience both as a GM and as a player the level of creativity a player has is not affected whatsoever by their GM. It's affected exclusively by themselves, because, uhh... It's their creativity. If they wanna add a village, they can do that. If they don't, they wouldn't without a GM anyway. In fact I would almost wager you that if a group of people came together without a GM and a person just wanted to make a character, but felt they had to add more in order to look like they were contributing, it would actually be less creative and less fun than simply having the GM there who has all this stuff set up already, and is willing to take suggestions from those who want to add more than a character.[/quote]

You'd be surprised. In my experience, I felt I had a lot more creative freedom in the GM less RP we played, simply because... well, there wasn't anybody around to shoot ideas down. In an RP ran by a GM, a good GM, of course players are encouraged to be creative and add and contribute to the world, but like you mentioned, a GM's job is to make the world and story coherent, and sometimes that leads to a situation where a player's idea is shot down. Done maybe once or twice or a few times, and even if it's done politely, it can be a massive blow to that player's confidence and creativity to the point where they might wish to stop trying based on only a few small ideas being turned down that don't fit, and which in turn would leaves more work for the GM. Of course that's down to the player themself and how they respond to that, but in a GM less rp you tend to not come across the situation where ideas are turned down. Although you do run the risk of a drop in quality of world/plot coherency. 

I still think a GM ran RP is better simply for the coherency of the world and story (depending on a player's standards and expectations for that), although we did a pretty damn good job in our GM absent one about keeping a well structured and coherent world, but again that was down to the group and our communication between one another, which can work just as well within a GM ran one. They both have their pros and cons, I guess, but it depends on the RP, the RPers involved, and even the site itself, I guess.