I still shop Amazon for many categories, but my guard is always up. But for some categories like apparel, the Amazon experience is so horrible that I don't even think to look there.
This discussion does highlight the issue though, we all had to go check, and check a number of different options, and are we still REALLY sure that we're getting an Anker product? Now, if you're my mom and you're not checking the right boxes and looking for the 8pt font of who it's being fulfilled by, what's your success rate with high counterfeit categories?
Bottom line, if I'm buying a brand, there should be NO DOUBT that's what I'm getting. Do you doubt the brand that you're buying when you walk in to Best Buy? I don't. When the prices are the exact same, I'm buying from Best Buy. If the price is significantly lower on Amazon, then I get super suspect about the authenticity.
Just bought a part for my Dyson vacuum cleaner and I found a number of suspect listings before I got the the one that seemed authentic- catalog shots, posting copy, lack of "Engrish". I was completely expecting to have to return it when I got it, but to my relief, it came in an "Authentic Dyson" labeled box and the fit, finish, color, and production seemed exactly the same as what came off my vacuum.
That's too much doubt for my liking.
edit: here is some discussion. FBA vendors appear to have control:
https://www.amazon.com/gp/help/customer/display.html/ref=hel...
But I still don't think the amazon customer can see if an fba vendor allows commingling.
But, no, we can't tell if a vendor commingles, we can only infer it in special cases like Anker as manyxcxi noted, or pick out vendors with high ratings and otherwise cross our fingers.
It's a colossal mess, and nowadays, if I'm not buying used books (where I go with < 95% rating and Very Good quality), I find a BS detector honed for decades, literally about 4 and half, is the single most useful tool in navigating their swamps. Which for me confirms they indeed have big problems, and that's not even counting their search engine, which as others have noted is bad; for me, by far the worst I regularly use, and like others I often use Google's instead.
All this implies to me that if AWS wasn't such a money machine, Amazon's stock holders ought to be very nervous. The company really need to get serious about these problems.