I've heard that books also have a high counterfeiting rate on Amazon. Over lunch with Paul Horowitz a couple of years ago he mentioned that he's had to fight to get counterfeits of "The Art of Electronics" taken down.

I read on here a while back about FBA inventory getting comingled, but I'm unclear on whether Amazon's own inventory gets comingled as well. Anecdotally I haven't received a counterfeit of anything shipped and sold by Amazon.