While I was away... Amazon clarifies its review policy

While I was away...

Amazon removed some of my reviews and explained in an email that this was "because you received compensation for writing the review." Feeling somewhat disturbed since I have never received any compensation for reviewing books, I pressed the "help" and "contact us" buttons on Amazon and asked what they meant. Amazon were very quick and helpful, and very patient with my repeated requests for clarification. So here, for anyone else puzzling over the mystery of the vanishing re...