The writer advises people to "look at the seller," but Amazon's commingling of products means that doing so is often useless. I believe I've also seen mention that there's a way to prevent that by assigning your own numbers and paying Amazon more, but for something like this where there is only one legitimate supplier I'm not sure it would do any good. (edit: NathanKP posted relevant links as I was posting)
What's amazing to me is that these days I'd consider eBay a safer option for a lot of purchases - at least there I know what seller I'm dealing with.
When I learned of the commingling they do I changed my mind about using FBA to list some products. It has also changed my mind on products I purchase when I see others are selling it FBA. Though I still use Amazon a lot, I have also increased my local shopping for products I would previously have just purchased from Amazon.
You need not pay Amazon to label your products with your FNSKU to avoid commingling -- sellers can do themselves with a printer and tape. Amazon simply offers the option and charges $0.20/unit to do it.
But if you're already the only legitimate source for that SKU what do you do? If a counterfeiter orders one of your items then duplicates the packaging including the SKU/UPC will it get commingled with your product even if it shouldn't?
What's amazing to me is that these days I'd consider eBay a safer option for a lot of purchases - at least there I know what seller I'm dealing with.