While I've been thinking about this a great deal personally,
delphic's quips about the rep system in the What kind of repper are you thread sparked me to make this thread. The main question I want to be discussed is: "Should websites who host users' pictures, comments, videos, etc. be held responsible for that content and the actions of their readers/members who use it?"
I would be inclined to say that they're not responsible to anybody but themselves (as an organization), but I could see where somebody posting a terrorism recruitment ad on Youtube, or photos of Palestinian prisoners on Facebook could be controversial, or Wikileaks being held responsible for informant deaths.
What do you think?