I've attended many a useless conferences. Then again, I've probably been responsible for running useless conferences as well - now that I think about it.
Seth brings up some excellent points in his post that just make sense. But even though what he says is true, human nature is the stopper. You can tell someone exactly what they need to do to get the desired results or avoid undesirable results, but human nature, doubt, emotions, etc. sways our thought process and actions.... and we continue to do things wrong anyway.
No doubt a lot of people will read Seth's post, and think to themselves, "Hmm, that makes a lot of sense." Yet the next time they run a conference.... it will still be a "useless conference".