Schizzo would be played by Jack Black. The studio execs don't trust the rabble to bring in the box office returns they need. They'll buy your script but not your crappy wannabe actors.
But the idea has potential. Only problem is, message boards are 2001. This one is a dinosaur that refuses to go away quietly. It would need to be a love of his Facebook wall and associated updates/friends/drama/etc. Or the woman he's been stalking on it for years.