Every once in a while, one of my friends gets wind of one of those facebook pages that promises a free iPad/Xbox 360/electronic device du jour simply for "attending" a virtual "free giveaway event" and sending invitations to all of your facebook friends. As far as I'm concerned, those pages are the worst possible combination of spam and computer viruses.
Is there any way to block or preemptively reject these kinds of invitations? I'm sure the operators of these things are too loosely organized and fly-by-night for facebook to actually have an option for this, but there must be some kind of workaround that doesn't ruin facebook's core functionality (i.e. I'm not interested in the "delete everyone from your friends list" option).