When I'm talking about "rules" I'm talking more about the intense sort of thing you'd find running in the background of some RTS game or Civilization. Like resource production algorithms and devoting most of the actual writing to number crunching. And then the gimmicks that begin to limit the scope of an RP to where it becomes really very narrow and not very free.

Detailed worlds and some defining of what people can and can not do (because there will always be those types that go out of their way to claim to be the biggest bad ass) is fine and all. But there needs to be a balance between keeping the RP open enough that people can come in with whatever they want (pending lore restrictions in a late-game setting), but keeps people in line. But if I have to read a forty page manual about how you're going to run the algebra that tells me what I can or can not do I'm not going to partake. I don't have the patience for that, and all I want to do is tell a story within the setting.

The rest is something of a community moderated thing, where if in relation to everyone someone feels too OP they can all voice their concerns and talk it out. Or make it an issue the GM will have to reconsider the guy's character or faction.