I think it would be really informative if we were to have a sub-forum for people to tell their horror stories about clients and whatnot, not to flame bad clients or anything (which I guess is sort of unavoidable, given the subject) but to let everybody else learn from their bad experiences. Setting some ground rules about not naming names would probably keep things more civil.
Learning from mistakes is the best way to know how NOT to do something - no reason people have to keep making them in isolation!