But even aside from hair-whitening legal issues, this is no answer. Vigilantes, though they start as a solution, always become the problem. In fact, the line between vigilantism and griefing exists only in the vigilante's own mind.
So must online communities resort to the old standby: police, laws and punishment? Are we just repeating the settlement of the Wild West?
Maybe not - or at least, not only that. As networks grow to encompass more of our lives, we'll develop routine access to people's records of past behavior. We could imagine a Griefer Standard, a defined data format game companies might adopt to identify and characterize griefing players. These players, after all, cost these companies a lot of money in support calls from victims. If a game's Terms of Service permitted the company to share your interchangeable Grief Profile with other companies, players' complaints against you might follow you from game to game like a criminal record. Games could allow griefers, but automatically red-flag them. Online game communities could then adopt social practices older than laws, and perhaps more effective: shunning and even ostracism.
Couple breakers have been around a decade, and disease carriers have only been recognized for a century or so. But many forms of griefing are as old as humanity. But online worlds have new tools at hand, and need not resort to the established legalisms of meatspace society. Game worlds can become the laboratories for new social systems, which may turn out to work - why not? - in wider areas of a networked society.
It's worth a try. Let's give it a shot.