Great article from Jamais Cascio, which describes Griefing, and as I recall Second Life has had its share of Griefers who have disrupted events, damaged and defaced in-world builds and developed & deployed massive code attacks.
Some Griefing can be akin to real world peaceful protesters however like phishing & viruses which are created by mainly criminals for monetary gain, Virtual Worlds are susceptible to criminal intent. Virtual Worlds like Twinity which is offering REAL world experiences in a Virtual 3D Online environment will need to develop and deploy monitoring and protective services either in partnership or directly to protect its members from criminals and Griefers alike. Article excerpt below:
The Griefer Future
Griefing is, simply put, making someone else’s online game session miserable. It’s not simply beating someone in player-vs.-player competitions, or even annoying someone as the side-effect of otherwise game-focused actions. Griefing means taking action intended to harm the game-play of someone else—these can include attacking someone ostensibly on your own team, blocking passageways, intentionally crashing your vehicle into someone else’s, leading masses of monsters to attack unsuspecting players (”training”), using known software bugs to force another player to “crash out” of the game, and so forth. While many of these might happen by accident, griefing is all about intent.
Read more: IEET