Due to the way Amazon commingles their stock at the SKU level, there is simply no way to guarantee that what you're getting is genuine, even if you order "sold and shipped from Amazon".
Even from an authorized retailer - the first thing I do with any flash card is fill it full of a test pattern using f3write, and then validate that it actually reads out fine. Counterfeiting of flash cards is absolutely rampant.
Newegg is probably still OK too, although they are now fronting for third-party retailers I haven't heard of them commingling their stocks yet.
And as a reminder since you mentioned them explicitly, a USB charger counts as 110/220V, not 5V.
https://www.bunniestudios.com/blog/?p=918
I do the exact same smoke-test - as I mentioned I use f3write to fill it full, and the counterpart f3read to read it back and test it.
http://oss.digirati.com.br/f3/
There's no official Win32 distribution but it compiles and runs without issue on Cygwin. When I get home, I can send you a Dropbox link with a build and enough Cygwin DLLs to make it run in a standard Windows command prompt.
As mentioned on the f3write site - one of the very typical hacks is to make the controller report a larger capacity than it actually has - or a larger capacity than is actually functional/reliable. So this is the obvious test to perform - write it full and see if you can read it out.
Amazon will co-mingle their stock with third parties as long as the stocking unit (typically UPC) matches. So if some retailer sends them fake memory cards you get a fake memory card, "Sold And Shipped By Amazon.com". And of course eBay is full of this junk.
At this point I prefer to buy from camera stores. My theory is that since their customers will be making their livelihood off the memory cards that they have an additional incentive to keep their supply chain clean.
https://9to5mac.com/2016/10/19/amazon-fake-apple-chargers-ca...
https://www.forbes.com/sites/amitchowdhry/2016/10/23/apple-n...
Apple has the clout to force Amazon clean up their listings, most manufacturers don't. Why does Apple have to coerce Amazon to do this, instead of them being proactive?
http://web.archive.org/web/20160609091210/http://salesresour...
Because, crucial, Amazon also comingles reviews for the same product.
I'd assume they have boilerplate in their legal agreements that waive rights to do so. But it seems blatantly obvious that if I put a novel item on Amazon, attract great reviews for its high quality, get comingled with counterfeits, have my reviews bombed by pissed off customers, Amazon has materially injured my business through no fault of my own.
They're already swimming in reviews. So I can't see them not getting more than they're losing by empowering customers to torpedo bad sellers.
Of course, this would also mean fundamentally changing their logistic practice, which is probably why they aren't interested in doing it.
This is true, and Amazon admits it. Co-mingling is a large part of their delivery platform.
If you send items in to the warehouse with the UPC, they will be considered co-mingled which means anyone else sending the same product with just the UPC will all be stored together. THIS is where you have the issue of the possibility of buying counterfeit products.
If you send the items in with the FNSKU, they will be considered separate from the co-mingled inventory. Anyone that buys from a seller that has the FNSKU will get the items THAT seller sent in, and not from the co-mingled batch.
For retail items, it's really up to the seller how they want to send the items in. For the sake of seller metrics, it would be wise to send in items with an FNSKU so you avoid the issue of a customer buying from you as the seller, but possibly getting a counterfeit item.
To clarify another incorrect statement in this thread: Amazon does not charge extra to not co-mingle the items. They do offer a service where they will add the FNSKU label to your items at .20/piece, but that's only if the seller doesn't want to do it prior to sending the items in.
Source: I'm a seller on Amazon.
If not, these specifics don't really matter
Buying from first-party sellers may help but even then Amazon doesn't always ship YOUR inventory. If the "same" product is physically closer to a user than yours, but they bought from you, they might ship from another seller which can be counterfeit.
cookware, phone charger, headphones, power supply, phone battery, SD card
I once used amazon almost daily so this is only a fraction of my purchases, but the fakes tend to be on expensive stuff. The convenience is not worth the chance of getting something worthless and I've stopped using amazon for anything.