this won't work. people will start using this board as a revenge tool. moreover, the admin will get a nice load of attorney letters once an innocent site is posted as a "spammer". you'd better have a fire-resistant ass because you're gonna get lots of heat
not to mention that a vicious spammer that gets exposed will simply forge a few lines in a message source, report you to spam cop and you're dead meat.
spam is part of this business. you'd better get used to it and let the gov't take care of it.