I wonder if reviews should have a field for "how long have I owned it" (or even "about when did I buy it", to track changes in manufacturing quality). Places like TrustPilot would probably benefit from coming back to people and saying, "Here's a review you wrote a year ago; anything you want to add?"
Manufacturers could even submit an "expected lifespan", and reviews could be marked where they were made within that lifespan. A bad review after 7 years of owning a 5-year product shouldn't count as much as a bad review 7 years after owning a 10-year product.
The point remains that you don't need to "buy" reviews. You don't need to give out coupons, or gift cards, or rewards or in fact anything. Hence why I said "it's not that complicated" as per:
> You've got stores that would include a $5-$20 coupon/gift card in the item in exchange for a positive review.
Why pay for what you can get for free?
Note: I did not last long in this business before hitting the eject button.