[ikeboy]

>Without that label, when a packer scans an item just before they place it in a shipping box for the customer, how do they know which seller's inventory to decrement?

It's very simple: they're stored in different locations. If seller A is on shelf B, and seller C is on shelf D, then even though the individual items are identical, if you pick up a unit on shelf D you know it's from seller B.

They don't store identical products from different sellers next to each other.

I agree there's a counterfeit issue. Amazon agrees there's an issue, and actually has it as a risk factor in their financial reports. But commingling isn't a significant contributor to it.

[secabeen]

That could work, but it's fairly brittle. If an item comes out of its location, you have no idea which seller it comes from. If an item is pulled incorrectly, and then set on the return-to-stock pile, you have no idea where to put it. Perhaps that is the issue; there are two copies, the counterfeit one gets pulled incorrectly, then when put back, they put it in the amazon.com location.

[ikeboy]

>If an item comes out of its location, you have no idea which seller it comes from.

You can check if the location it was supposed to be in is empty. From my understanding, the main issues happen during receiving; if it's received to the wrong shipment it'll be incorrectly marked in the system and unlikely to be fixed. Once it's received to the correct system everything else is fairly robust.

>If an item is pulled incorrectly, and then set on the return-to-stock pile, you have no idea where to put it.

If it's pulled, then there'd be a record of where it was pulled from, and that place would be empty.