> No idea what do to about the reviews,
They need to patrol the sources for fake reviews (facebook groups, etc) and perform sting operations to catch the sellers who solicit them. It shouldn't be too hard, a simple Facebook search finds hundreds of groups and thousands of solicitations. Once you identify a seller that does this, you ban them from Amazon, as well as everyone who's given their products a fake review (for the reviewers, it should probably be a three strikes thing before they're banned, since a lot of them seem to just like free stuff).
> but the first step to the counterfeit goods problem is simple: once you've received X complaints about a counterfeit product, stop selling the product.
> Continuing to sell a product for which there are numerous and credible indications that they are counterfeit is borderline fraud.
I'd say the second step is to roll back many of Amazon's practices that make counterfeiting harder to detect, for instance how they can commingle inventory between sellers (if those sellers weren't careful when they made their listing). That makes it impossible for the sellers to have meaningful reputation scores, since bad-actors can sell their counterfeits through honest-actor storefronts (and vice versa).
The third step is to implement better supply chain management and vetting of suppliers. Not everyone should be able to set up a marketplace store and sell any product. There needs to be effective vetting of sellers and it should be hard enough to setup a marketplace account they can't just create a new one when their last one is banned. There should also be especially stringent vetting around listings for frequently fake and counterfeit products, like SD cards.
The fourth step is to implement active counterfeit and fake product detection (through test purchases). If a particular item is too often fake or counterfeited, Amazon should ban it from the marketplace and only sell inventory directly sourced from the original manufacturer.
None of these things should be too hard for a company with Amazon's resources to effectively implement. The fact that it hasn't says that these problems aren't a priority for it.