I worked in the Amazon warehouse for a while and (if my memory is correct) for this to work, Amazon would need to have a dedicated area for each vendor so that all vendor X goods are in bay Y, for example but costs would soar!

However, they currently don't do that - Everything gets put anywhere there is space.

There are some areas where stuff is put all together, like for example, there may be a shelf space full of a particular brand of superglue. If more comes in, even from a different vendor, as long as it is given the same ASIN (I think that's how it works - the ASIN is Amazon's internal ID system, sort of) then you can put that superglue with the other superglue in the same shelf space. That means you don't know who's superglue came from what vendor!

So if you received fake superglue and it came out of that shelf with superglue from 10 different vendors, which one sold you the fake?

It's a brilliant system all round: storage is cheap so the vendor doesn't pay high costs, Amazon keeps their costs low as their storage space is fully utilized.

The downside is that counterfeit orgs know this and it's easy to game!

Amazon can legitimately say that they don't know which vendor is the guilty party and no one can prove that vendor X sent in dodgy goods. Not sure if that's a legal defense or not but they have lots of money and you don't!

In fact, I remember someone a few years back on HN mentioned they were kicked off Amazon due to selling counterfeit DVD's (maybe CD's!) even though they were co-mingled so there was no way to tell.