City of Heroes, a multiplayer superhero game, decided to allow its users to design their own levels. While some users created some fun and imaginative levels, the majority produced incredibly easy treasure-hauls, the sort of quest we used to call "Monty Haul dungeons" in the D&D era.
There's something weird and paternalistic about the relationship between gamers and game-designers. It goes like this: "I will deny you reward until you complete some arbitrary tasks of my devising, because I know that this will make you happier than simply giving you the rewards right away" (what's more, the designer is generally right about this).
This authority and arbitrariness is simpler to navigate when you're playing D&D with some friends around a table -- the GM is a pal of yours in whom you've put your trust for a few hours, and if she doesn't deliver the promised fun, she can be ousted and replaced. The GM doesn't even have to stick to the rules: if she thinks that the game's fun will go up if she ignores the outcome of a dice-roll behind her screen, she can make up an epic save or fail.
But it's different when the "GM" is a bunch of rules programmed into a computer by an engineer working at a multinational. In that universe, if the rules are bent for the sake of fun, it's cheating. And the social contract that comfortably defines the relationship between friends stretches and tears when it's applied to the relationship between customers and corporations.
When City of Heroes released its user-created mission generator, it was mere hours before highly exploitative missions existed. Players quickly found the way to min-max the system, and started making quests that gave huge rewards for little effort. These are by far the most popular missions. Actually, from what I can tell, they are nearly the only missions that get used. Aside from a few "developer's favorite" quests, it's very hard to find the "fun but not exploitative" missions, because they get rated poorly by users and disappear into the miasma of mediocrity.
This was not what the designers hoped for. Somehow they had convinced themselves that the number of exploiters would be relatively low -- certainly not the vast majority of the users. But they were wrong, and now they're stuck between a rock and a hard place. They feel they must counteract these abusive quests, "for the sake of balance". But how? Well the first step is to ban people who make cheaty content. But what's cheaty? Do they explicitly list every possible exploit condition? What if they miss one? Nah, then the problem would start all over again. Instead, how about if they just issue blanket threats that they'll ban missions that seem "exploitative", without actually explaining what is and isn't "exploitative"? They went with the latter.