Blocks, my man. Blocks. That's why we were talking about them yesterday. Requesters can screw your world with a click. Occasionally, they can even do it on a whim or by accident. Blocks and internal metrics(based on performance on Amazon HITs(imo), and other secrets) can cause you to lose Masters. But, 2 or 3 Blocks in a short time and I'm pretty sure you'd lose it. Once again though, this is all supposition without confirmation from the powers that be.
EDIT Like I said, Metrics on Amazon HITs. This is an example of why I think that people in non A9 states have a harder time getting Masters, imo. Don't want to argue it though. I don't feel strongly enough about it to care.