Recently I saw an item where the warranty would only be valid for the Sold by Amazon version. The first bullet in the product description was "Amazon as the seller is the ONLY authorized Fulfilled By Amazon Dealer".

I ended up buying the item in a brick-and-mortar store -- same price, instant pick-up, and easier to return in case it didn't meet my needs (plus no fear of blacklisting or whatever, which I'm not sure is a thing Amazon does, but I don't really want to find out, either).