That's really sad because it is a form of blackmail. If I were the seller, maybe I would publicize the message of the buyer so the bad reviews wouldn't have an effect on my business albeit it would be a propaganda. As an advice to those ebay sellers, when you encounter a blackmailer, do not be afraid if your business is on the level. Just go with your process and be ready with a press release to rebut the claim of the blackmailer. Bad reviews? They come along all the time and the question is do they have readers?