A group of technically sophisticated trolls, the W-Hats, from Something Awful unleased a doomsday device (a few times) on the virtual world, ruining the experience for everyone. It was essentially a fork-bomb, which overwhelmed the servers of the game, Now the proprietors of the game are talking "FBI". This is covered here.
A previous hack, by the same folks, involved hacking a client so that they could violate the protection scheme of the game, stealing the source code of valuable in-game objects/businesses.
The interesting thing about the responsible trolls is that they've combined technical skills with anti-social behavior multiple times -- the doomsday device is just their latest. Previous "offenses" have included: Building offensive structures[NSFW!!], extorting money from neighbors, or mocking the 9/11 attack on the WTC.
So this is a virtual world where trolling and hacking have financial consequences -- not just for the proprietor of the world, but the players, whose "virtual property" can lose or gain value based on the actions of trolls.