Ah, you guys have certainly given me a lot of meat to chew on. ;)

In clarification, I am thinking about an online RPG genre game, which feels pretty overdone these days. That should inspire me to look elsewhere, but them's be players in dem genre!

WiseElben: If I were to do this, I would ideally want the playerbase to be not overly huge (< 150), but still enough that the level of content matches the level of players.

Stru: I could start up a team and make a "normal" game if I chose, but I found this particular method very enticing. I do like your idea of specifying what sort of content I required and request only that, but I think it would kill some of the creative flow that I would want the players to have.

Nairb & liquiddark: Thanks! I'll check out both of those.

hplus0603: MUDs usually work it differently. Usually the builders are people chosen to be on the staff that have played the MUD for a lengthy period of time or have been hired from their past building experiences. I want to leave the ability to add onto the game in the hands of ANY player.

To be honest, it sort of stemmed from my days of playing various Diku MUD derrivitives. The derrivitives usually hold a world that is made up of tons of areas made from different people throughout the course of the codebase's lifetime, most of which never met eachother. Yet the world still is fairly consistant as long as the theme is general enough (such as fantasy).

Thanks a lot for your quick replies, I'm looking forward to more. :)

A quick thought: it might be interesting to impose a sort of feudal system, where some players are responsible for others, and there are several levels of this. The people higher up the hierarchy get some benefits from content produced by the people below them, and those people gain some sort of protection/mentorship/etc from their superiors.

This would create incentives for players to create things that fit the theme of the game, and empower the more advanced players to pre-screen a lot of that content for you, making your job easier.

Wouldn't work as an MMO, for the play balance reasons outlined above. However, if some sort of local game with a metagame content-rating-creation networking system, I think that would do well. Blizzard succeeded wildly with their simple level editors in the *craft games integrated into BNet, and UT's mutators are another good example of prevalent user-content.

Edit: more detailed explanation of MMO problem. Any artificial content in an MMO is instantly "in the wild". Unless there are ways to do "limited release runs" of content, and bad content will be stopped somehow (or there's a powerful play-balance system in place) then the world will be flooded with crap. Second Life does this - you don't have control over the "power" of your global content, and scripted content is usually only allowed in limited "zones" - if you want to make rayguns, you need to get some turf together that is a "raygun zone". Players pay real money for such priviladges.

So I prefer the match-based games. Stupid stuff gets ignored by players, who just don't run it in their servers, or don't play on servers that use it. Still, it all has to go into some giant content-management system. The trick is this: players produce stupid shit, and the easier, the stupider. So, you need some way for the good stuff to bubble to the top, without squashing the innovators who don't want to make the 1000th MP-5k that 90% of all players demand.

Second, you need content to be easy to make. That's a given, but nobody's done it yet on a large scale (except maybe Virtools). Al that's been done so far are simple map editors and the like. Component-based design is a must.

Third, content must be very, very compact. Lossy everything. Try downloading 20megs of texture data for one player model in UT, and see how it feels.

I would think that this is definitely possible.. After all, one could say that it isn't much more than an extension of a typical open source project.

If I look at your concerns, most of them do apply to code as well. If you let everyone check in code without review, you will end up in a mess. People could also try to put in backdoors so they can cheat. And so on...

I think this is possible, the question is indeed how much you will want to regulate this. I'd say thoroughly review everything as much as possible, as it'll be better to have a smaller amount of good content than a big amount of crap.
Of course, balance will be a problem, so I'd say it should be such that they can design everything but the rewards. I don't like the idea that the same monster drops the same item everytime anyway (as an example), and if you make this random, then the one making the content can't really do that much to unbalance it.

Coordination between people working on this will be a problem as well, but again: Not any more than with code.