When you put incentives and penalties on player actions, and attempt to give people tools to create a social agreement on how to appraoch your game, you are building a biased social platform.
(A big goddamn caveat, here: Note that I am NOT saying now, and have no intent to say, that the fictional material of your game is a significant part of that engineering, that violent fiction does thus-and-so. I don't know such stuff.
In Matthjis' thread, the Stanford Prison was mentioned, and the Milford thing. Those are pretty extreme examples-in-point. However, I'd like to point out something a little milder; while the extreme examples show a point, they show it "out there".
Take a gander at this wiki article: Broken Windows
The idea is simple. The context in which people operate changes how they act. It changes how they act a whole lot, and it can change the way they act in pretty intense ways.
Sometimes it's about scarcity effects: A little Clay Shirky
Sometimes it's about authority over group intelligence: A little James Surowieki
And these are all thing we tinker with in gaming; Context, Scarcity, Authority, and Collaboration are a big deal in a lot of current game design precisely because they are effective tools for social engineering.
You, game designer, are a small-scale social engineer. And this means a few things - it means that maybe you can learn a whole lot from other discussions on social engineering. It may even mean that gaming will, one day, have something important to share with the world about group coordination (don't bet on it, but hey).
It also means that we, as designers, have some big scary places we could go, inviting others along for the ride. That's likely an exciting thought to some; it's also, likely, a repulsive thought to others. There has been plenty of griefing and vitriol spewed over smacking around the social boundaries of "Is this an RPG?" - imagine the confusion when some of us start pushing regularly and seriously into territory where the question of "Is is safe?" stops being funny.
I'm rambling now, and I'm not sure where to go from here. I'll happily defend this, if desired. Or someone else that's smarter or knows more can pick up right here and keep moving.
(Huh. I thought I'd use more links than that. Ah, well).