Comment by gambiting

"really cheap ones marked “BLOCKED BY AMAZON”; I decided not to go for these since theoretically they might have been stolen."

I'm not sure Amazon even has any way to report a stolen device to them so they can block it. I have a blocked Paperwhite(1st gen), because Amazon sent me a new one as a warranty replacement, but they specifically said that I don't need to return the old one - it's just blocked from accessing their servers. I imagine that's exactly what those cheap kindles on eBay are.