This is my greatest stolen modified idea today. Metafilter hitpoints! We all get 5000 to start. Once you level up via unattacked thread posting, you can cast healing spells on your favorite, but inexplicably hated MeFi pals, or do double damage with Fireballs. Anybody who reaches zero has their account closed, unless someone ells resurrects you by sacrificing 3/4 of their remaining points.