I wonder if they have any intention of going after Amazon - probably not.
https://www.ftc.gov/system/files/attachments/penalty-offense...
It's possible for big companies to "be involved" via third parties. For instance, Big Company pays Big Agency, who allocates some spend to Unscrupulous Digital Marketing Firm or Shady Digital Advertising Service.
This doesn't mean that Big Company intentionally engaged in bad behavior but on the other hand, big companies tend to work with so many third parties that "hear no evil, see no evil" and plausible deniability are built in to their operations.
Bear in mind, this is not just about "fake reviews" like people submit on Amazon. This is about "falsely claiming an endorsement by a third party; misrepresenting whether an endorser is an actual, current, or recent user; using an endorsement to make deceptive performance claims; failing to disclose an unexpected material connection with an endorser; and misrepresenting that the experience of endorsers represents consumers’ typical or ordinary experience"
I guarantee you both Google and Pepsi have committed offenses on that list, and so has nearly everyone else in modern marketing these days.
On Amazon it's easy: if it's got hundreds of reviews, it's probably mostly fake reviews.
Even for those products if you spend some time you'll find some nuggets of useful information in there.
Contrast with some furniture site I went to some months ago, where there are only like 5 reviews per product and all of them are so completely fake. They assured me the desk was "very stable" which should have tipped me off already ... Later I noticed this "brand" is all over Amazon and each of their products has hundreds of positive reviews.. they are so easy to spot on Amazon... not so much on other sellers where they rebrand the product, have ten times less product info in the description, less photos etc.
They are liable
But this is not an opportunity of growth for Amazon. It is not a business critical area either and certainly is not perceived as meaningful threat or weakness.
More aggressive investments in this area aren’t justified because it truly doesn’t have a clear effect on the bottom line.
Reputationally, I doubt they care. Amazon has hundreds of thousands of vendors who sell up to 12 millions SKUs to hundreds of millions of customers.
It just makes sense to invest in tools and programs for the hundreds of millions of legit interactions (including reviews) that happen on their platform, than focusing too heavily on those who are not playing by the rules.
Although it would be interesting if there were ever fake reviews on the Amazon branded products. (AFIK there aren't)
If Amazon doesn't want the responsibility of having to make sure stuff on their website is actually legal, then maybe they shouldn't have made letting everyone sell stuff on their site their entire business model.
They want all the profits of being a middleman but without taking any of the associated responsibility. It's a hilariously crap excuse.