Ever hear the old adage, variously attributed to everybody from Groucho Marx to Winston Churchill ...
GROUCHO (to woman seated next to him at an elegant dinner party): Would you sleep with me for ten million dollars?
WOMAN (giggles and responds): Oh, Groucho, of course I would.
GROUCHO; How about doing it for fifteen dollars?
WOMAN (indignant): Why, what do you think I am?
GROUCHO: That’s already been established. Now we’re just haggling about the price.
Perhaps my view on this is coloured by having spent 25+ years as a freelance journalist, including writing several thoussnd product reviews, but I wouldn't dream of amending a "review" in their favour if the company producing the product offered me a bung, and it wouldn't matter how big the bung was.
If I review a product, the reader ALWAYS gets my genuine, considered opinion based on an impartial examination and testing of the product. I wouldn't change that opinion if the publication asked me to (see note), never mind the company producing the product.
Clearly, a "professional" review by someone paid to test and review isn't quite the same as a user review, but nonetheless, my ethos is that if I give a "user review" that's amended for money, then it's more advert than review. And pretending it's still MY opinion is a deception.
Not once in that 25 years has the producer of any product ever offered incentives to colour a review. There were two or three times when I felt or suspected a remark might be sounding me out, but I either ignored it or obliquely shot it down ... and warned the editor of my suspicion.
If I'm writing a "review" that's better than my opinion honestly is, it's an advert not a review, and I don't write ad copy. If I did, it would be openly for ad's, not for ad's masquerading as reviews.
By "change the review" I mean change to tone, opinions or conclusion. I have changed the length of a review, where the product justified either a longer or shorter review, at the request of an editor.