I can buy the complaints about Search (though really it's a problem of having too much selection). However, I've had universally positive return experiences, so I have no idea what you're on about there.
a. If Amazon sells a 64 GB Sandisk card
b. Merchants A and B also sell the same card
c. Merchants A and B have opted into the fulfilled by Amazon program.
Question: You purchase the 64 GB Sandisk card and pick Amazon as the seller. Whose inventory did the card come from?
Answer: Undefined.
For semantic purposes we can think of the following mental model - For a given SKU Amazon takes the memory cards from its own inventory and inventory from all other resellers who have opted into the "Fulfilled by Amazon" program (in our example A and B) and puts it together in a giant heap in its warehouse. When a order comes in a card is picked at random from the heap and shipped out to you.
So for Sandisk specifically this isn't a concern, although your comment applies to other, unrestricted brands.
This listing came up in the top 10 when searching for "Sandisk 32GB": https://www.amazon.com/SanDisk-microSDHC-Package-Extenders-A...
The seller is "VP Distributor" and the brand is "Sadnisk" (sic). I don't see any links to see more info about the seller.
98% positive and 2250 lifetime feedback ratings means it's probably a good seller, just not authorized for sandisk and listed there to get around the rules. If someone took the time to report them the listing would be removed.
OTOH the same seller lists https://www.amazon.com/dp/B00M55C0VU, which I've confirmed on my account is restricted. So maybe they are authorized, and just listing on any ASIN they can find that matches the product? I've done that sometimes.
It doesn't look like customers are being harmed in this particular case, it's possible some unauthorized seller created the listing and VP distributor simply jumped on it at a later point, the first seller could be suspended now.
No. Sellers have to opt-in to co-mingle, so it's certainly not "all other resellers".
Besides, I think co-mingle only applies to resellers's stock, ie Amazon stock and 3rd party sellers' stock aren't put together in the same basket -- although I could be wrong about that.
If you buy the one that's sold by Amazon it will come from the stock that's bought by Amazon.
http://www.wsj.com/articles/on-amazon-pooled-merchandise-ope...
Do you have any sources which specify that Amazon treats it own inventory seperately?
I always use the "Amazon Prime" filter when I search, and I've never had any issues with those items. Sellers have to share a little more profit with Amazon to be listed as Prime, but I think that's enough of a bar to eliminate the fraudsters.
The only times I've had problems were with non-Prime sellers, but luckily those were just long-delays rather than outright fraud.