Co-mingling is a nightmare, even if you aren't an FBA seller. Amazon was a reseller for a product we launched on Kickstarter. Our product was a precision optic

Co-mingling is a nightmare, even if you aren't an FBA seller. Amazon was a reseller for a product we launched on Kickstarter. Our product was a precision optic, made in the USA. A few months in, a counterfeit knock-off of our product was manufactured in China and distributed in great quantity. The counterfeit items had the same bar code and nearly identical packaging (except it said "Made in China"). The knock-off wasn't optical quality and took lousy pictures. Third party FBA sellers were buying the counterfeit unit and stocking them at Amazon. These would appear as "Other Sellers" on our product page, and would usually be selected by default because of crazy low pricing. Amazon co-mingled the counterfeits with their own inventory of genuine goods that we sent them. They began to draw from the counterfeit stock for their own sales instead of the real deal. Customer reviews tanked. We figured out what was happening since we knew these other sellers weren't legitimate, and we received counterfeit returns. We were able to ask Amazon to shut down the sellers, but the tainted goods remained in inventory. Amazon was either unwilling or unable to screen their inventory to eradicate the counterfeit goods. Since they were useless in fixing the problem we just stopped selling to Amazon and labeled the product page as counterfeit.