I started mturk years ago and had rejections. Amazon said they were too old to do anything about so I worked hard to bring up my approval rate and almost had it where I wanted it. Then a .02 HIT was rejected! Reason is unacceptable. Requester won't answer and I'm surprised Amazon has no recourse. If you don't know "Mechanical Turk is not responsible for resolving any disputes between Workers and Requesters related to any Tasks or any transaction". If they don't feel like accepting or paying they don't have to. I guess I need to pay attention to the approval rate. That's the only way, right? Does anyone know if Prolific is any better?