Amazon is basically providing a goods laundering service for criminals. There's not much difference between what they're doing and what someone is doing who is fencing stolen goods.

If they're going to comingle goods, then they need to put their own tracking onto the goods so that it is possible to know who provided the goods to which buyers. Either that or require that each item has a unique rfid or other identifier. This would allow tracing of counterfeit goods back to the supplier.

As it is, when you buy something that turns out to not be legit, you have no real recourse, and often the wrong supplier gets dinged.