I feel like someone could do better than SomethingRotten though, by playing both sides, and encouraging users from both to brigade and annoy the shit out of your typical user. To the point that the users start asking themselves "what am I supposed to do here? If I support [cause], Reddit screeches at me; if I oppose [cause], Reddit screeches at me; and if I don't do either, both screech at me! Perhaps I should stop using Reddit."
This could be based on porn (perhaps a good target for that; as @remotelove said, who controls porn controls the internet)), or even some ultimately pointless matter, like pineapple on pizza.