Improperly used or inconsistently used they're right. Not that effective, but if you punish consistently and fairly it's super effective especially when you make sure to remove opportunities for the dog to reinforce itself on the behavior again.
It's one of those things though. Once you decide to open that door you should stick with it till the undesired behavior is done. Otherwise you're no better than the drunk dad that comes home every once in a while and beats his kids.