This is not a scam unique to Amazon. It happens everywhere, and has for decades at least. A more insidious version attacks eBay sellers. The buyer will send an item back broken and ask for a refund, meanwhile keeping the good verse;n you sent them. Take serial numbers, secretly hide marks and photograph them before sending anything.
But do you do with that serial number mismatch and 'missing secret marks' evidence? A seller could easily fudge that "proof" and eBay/Amazon aren't big on taking sellers at their word. There's no fool-proof way to collect evidence of return fraud and there isn't much you can do once you have that evidence.
