For all you Facebook users - there is a virus spreading through Facebook that has infected many users already. It basically comes through as an email or Facebook message with a subject line like "You're in this video" or "You're on this webcam", etc, etc.
When you click the link it takes you to a page where you're told you need to install a plugin to view the video. The plugin is, of course, a virus that does bad things to your PC. Read more here: http://www.techcrunch.com/2008/08/07/elaborate-facebook-worm-virus-spreading/
Also, there are other dangers coming to light. MAR IT Director Mike Cutlip provides more information about social engineering scams on Facebook, MySpace and other social network sites in this Tech Tuesday article
from December 2008.