I'm not sure if this counts as a player run event, but large scale invasions of opposite faction cities are something I've found enjoyable.

Only other thing I've seen event wise is a GM who loaded up a huge-ass monster and invaded a city.  However, I'm not sure I'd want to give players access to such a tool.

Originally posted by Scot

Play some of the mods in the Fallout or Elder Scrolls series, then come back and say they were not "fun". Yes you can get some very poor ones, but the best a top notch and most are of a high quality. Less well known would be the Neverwinter modding, they did some great stuff there MMO wise. Thinking back to AO were you could do some scrippting, the fanbase created a text based library for nanos.

Given the chance players can do a lot for a game, gaming companies do not tend to like it too much as it raises copyright issues. But many modders these days have their stuff brought in house so to speak, like in the Civ series.

I use to play NWN, Dungeon Siege .. both have mods .. and yes, 99% are no fun. And even the good ones are poor immitation of professional produced stuff.

There are some .. very rare .. good mods .. like DOTA ... but i would waste my time on 99% of them.

1) Devs can't make enough content by comparison to the time players can burn through it.

One game .. may be not. Just play a few games .. there are more than enough content. I will never have time to burn through content in DDo, LOTRO and DCUO.

Re: OP

The MMO I am a part of does this on a regular basis.  See:

http://massively.joystiq.com/2012/04/27/some-assembly-required-ten-years-warp-by-for-vendetta-online/

And also:

http://www.youtube.com/watch?v=tnYiqbciNiw

and:

http://www.youtube.com/watch?v=m4hM08fSLFY (voice cast by yours truly)

A big part of getting around the maturity bar required for having access to "GM" tools is 25 hours of game time logged and a 500 word essay on Maturity, Trust, Involvement, and English, before being allowed access to those tools.  However, most of the events don't even need the tools; as it is a sandbox environment the community tends to be self-organizing.  The "Nation War" that I voice-casted from last Sunday can be run by anyone, without any special privileges except for the trust of the community.

I don't see player modding as being needed for sandbox or themepark; they just make for a better game. But in a themepark where content locusts want a new serving every month it may help to whet their appetites.

How to fix its exploitability, Simple.

A) make the reward come from the inventory of the player who put it up.

B) Make the reward a Random Box

C) Scale the Reward with the difficulty of the mission.

D) Have the rewards have nothing do do with item progression and simply make it a Monitary Gain

E) Make the quest require a GM approval (Dont like this option)

There are plenty of other ways aswell these only fix the exploitable side of the rewards