This is not quite true. If I'm a bricks and mortar retailer, and I sell a piece of hardware, and say "Thanks for shopping with us", nobody can later refer to that "Thankyou", and see whether I thanked the buyer. When he comes back to complain, I get the chance to listen to his complaint, and fix it. If I do well, he'll actually be more loyal to me than if he had no complaint, and will tell his friends. Again, there will be no record sitting out there that he complained, but there WILL be the word going round that I looked after my customer really well. So goes it for the bricks and mortar retailer.

For the online seller, they sell a product in good faith, leave positive feedback, and the next thing they hear is a negative feedback, which is there for all potential customers to read, and can't be removed, saying "Product broke - it's rubbish. This guy is a thief - don't deal with him". Now, I might know very well that had the customer emailed me, I would either have replaced the product, or I would've refunded his money, and he would have been much happier, but he didn't do that. The only thing in my favour is that if I haven't posted feedback yet, he might wait til he's talked to me before giving me negative feedback, because he fears I'll retaliate. It's a bad system, but there are so many dumb buyers out there that for sellers, there's really no other option.