Amazon's customer reviews aren't all put together by thoughtful buyers: as it turns out, Amazon has a program that sends free products to some of its top-ranked reviewers in exchange for a write-up. The program is called Amazon Vine, and though it's been running since 2007, a new NPR report is bringing it some renewed attention. "I've had everything from very cheap earbuds, to $500 multifunction laser printers," Michael Erb, Amazon's current top ranked reviewer, tells NPR. "I've gotten a spin bike, which is probably valued at closer to $1,000."

A list of items determined by Amazon is offered to reviewers twice a month, and reviewers can choose two items to receive from each list, reports NPR. They receive the products completely free, so long as they agree to write a review within 30 days and never sell or give away the product. "If you were just to add it all up," Erb, who has been in the program for five years, tells NPR, "It’s probably thousands of dollars worth of stuff." Amazon is also able to ask for the products back, though Erb says that hasn't happened with him before.

While Amazon does make details of Vine public, it's still far from being a widely known program. "It’s kind of like Fight Club, you know?" Erb tells NPR. "You don't talk about it." Reviewers in the program have all of their write-ups tagged with a small label that says "Amazon Vine Review" and another that says "Vine Voice," both of which offer links explaining what the program is — though it wouldn't be hard to glance over them.

It's easy to imagine that being provided with free products might positively swing Vine members' reviews, but Amazon says that this actually isn't the case. In a statement to NPR, an Amazon spokesperson explains that Vine reviewers give lower scores than the average customer on the site. "Our theory is that it’s because they take that role so seriously to give as much unbiased perspective on reviewing that product," the spokesperson said.

Even so, Amazon reportedly says that a product with bad reviews still sells better than a product with no reviews. NPR reports that Amazon capitalizes on that by specifically courting companies with products that haven't received a lot of reviews into offering products to its Vine members. It seems that no matter what their take is on the product, it's good news for Amazon.