alt Hacker NewsYou approach that from a game design perspective to reduce the reward and set bounds on how much fun a player is allowed to destroy maliciously and what kind of counterplay is available, but if you completely eliminate it the world loses a lot of its drama. Conflict drives narrative.
I know Raph Koster has spent a lot of time since he designed UO thinking about this problem. I haven't looked at his current project but am curious to what extent he's licked this issue.