I have a rule of thumb regarding unsolicited PMs from people I don't already know. If they have 0 posts, that's an automatic delete. If they have any posts at all, I go back to read what they've said in the forums.
I guess that's where I screw up as I usually answer every PM with something. I should use you're rule because I am tired of "I want to lick you ass" fifty times a day. I should delete my avatar too I guess. I hate creeps!