Bunch of people report Amazon as being rife with fake reviews. FTC puts together some sort of working group that does some research to figure out if it's true. If it's true, they reach out to Amazon telling them to fix it after handing them a fine. After a while, they verify that Amazon implemented sufficient safe-guards against fake reviews.
Sure, it wouldn't get rid of all fake reviews, but surely it'd be better than the current approach of doing absolutely nothing, no?
Of course they want it. It's purely objective for them and purely deceptive to the consumer. Therefore, it's the perfect thing for the FTC to regulate - I mean this is what their purpose is.
Enforcement will be difficult, but I really think platforms like Amazon isn't the problem. They're a unified platform, it's pretty easy for them to enforce better review. Maybe you need to have actually bought the product, maybe they monitor product descriptions for asking for reviews, maybe they audit packages for those little "review us 5 stars!" slips, maybe they prevent modifying products, etc.
The true tough thing to enforce is little shops. You know, convenience stores, smoke shops, that type. I've been told, verbally, many times that if I review 5 stars, I get some discount. I doubt the FTC will send physical agents to check that.
But, I think most online buying in the US goes through Amazon and maybe a couple other online retailers. Fix it there and you fixed the problem for 90% of cases.