call the cops...if they don't do anything then get even.
But wait before you do anything...like 6 months or so. That way it can't be traced back to you so easily.
Also, after 6 months you may cool down and decide it's not worth it. If you're still pissed after 6 months then they probably have it coming.
Things have away of evening out, also. A guy on here who i bought something from proceeded to blow me off when i complained that the deal wasn't fully consummated.
Saw a post of his recently griping about his engine getting blown.