It's an odd thing. Over the past year my wife has gotten a ton of stuff for free or near free. She just posts a review, indicating she was paid to do it (important). One example site is amzreviewtrader.com. It's so awesome to get so much stuff for free/cheap.
However I'm not sure it is good for consumers. She is honest in her reviews. But you are evaluated for each item you request to review, and it would be easy for an unscrupulous reviewer to only post positive reviews to appear as a better candidate.
At this point, it is so prevalent, maybe it's time for Amazon to offer something similar with tighter restrictions.