Comment by mikeash

You can pretty easily observe that they aren't. Try to find a company where googling the company name shows you a top result that is actually another company with a storefront selling the same products. Now try to find an Amazon listing for a company's products that includes a third-party seller.

It's easy to see why. Google's entire reputation is based on providing good search results, to the point that "to google" has become a verb meaning to search the internet. They put a vast amount of effort into ensuring that they provide good search results. It is possible, with nefarious SEO and such, to beat out legitimate results sometimes, but it's not easy or reliable.

Amazon, on the other hand, doesn't seem to care. Sign up to sell a product, done.

Why would a liability rule kill Amazon? They can make it a part of their seller agreement that the seller indemnifies Amazon for all liability. This is different from making the seller directly liable because if the seller bails out, Amazon it stuck with it. This means that Amazon will have to make sure they can actually get satisfaction from sellers. There are many ways this can be accomplished, such as requiring the seller to have liability insurance with sufficient coverage.

I'm sure that such a rule would result in Amazon losing a bunch of tiny, no-name, untraceable sellers. Which is, of course, the whole point.

How is failing to ship the item or charging too much worse than counterfeiting? Both are trivial to counteract: initiate a chargeback with your credit card company. The same is true for counterfeits, if you detect them. The whole problem with counterfeits is that it's hard to detect them. If it was easy, this whole thing would be moot.