Trust no one
We are bombarded by fake reviews in all walks of life. I don't see much that Amazon (and, even less, Google) can do about it. I searched "get paid to review amazon products" and got 1,780 hits on that exact phrase.
And I'm not sure why the competition watchdog chose this bone to pick. Of all the things I'm concerned about with Amazon, fake reviews are low on the list.
Caveat Emptor