And there's the rub: as long as the item is good quality. The main reason for trademarks, economically speaking, is to increase information flow in the marketp

And there's the rub: as long as the item is good quality. The main reason for trademarks, economically speaking, is to increase information flow in the marketplace. If some seller claims they have good quality products, you have to just trust them; if they have a trademark and you know that they have a reputation for quality, that trust can be much more accurate. Where Amazon messes this up is in the intermingling of reviews and inventory for genuine and counterfeit trademarked products, so that customers can't tell whether they're getting Apple-quality or random-Chinese-manufacturer quality chargers, which will either be super-safe or will blow up their devices. I'm totally okay with buying a battery from a third party, as long as the real manufacturer is clearly indicated and I can check up on the reviews of their build quality.