To be honest, if I were a wealthy or powerful attorney, I would hire some researchers and sue the fuck out of all the rumor starters on a class action level in multiple different suits. There are clearly ways to investigate and trace these things.
I can't even imagine how much money has been made/lost due to these purposeful rumors...it's seems clear that half of them are just to push stocks around...the funny thing is that it seems like once they go up post rumor, they just stay there and don't even come down.