Amazon has been incredibly successful in leveraging crowds – in the form of its own customers – to review products sold through Amazon.com. The reviews create value for both sides in the marketplace. Customers can rely on reviews to research a product before buying, filter purchase options with minimum rating levels. Sellers benefit from a free marketing boost if obtaining many positive reviews and also get direct feedback from customers on how they perceive the product. Finally, Amazon itself captures value by providing an easy way for customers to evaluate purchases on its platform and by boosting traffic to well-performing sellers (which helps minimize customer complaints).
So, 5-star products are all good – right? Not necessarily!
Sellers have high incentives to manipulate their reviews, either to boost ratings of their own product or to drag down competitor ratings. Amazon has even seen politically motivated review-manipulation. Just a few hours after Hillary Clinton’s book “What Happened” had been released, the book quickly received 1,660 reviews which were either 1 or 5-star ratings. Amazon later found these to be fake and removed them . Other fake reviews are more innocent of nature (I in particular like the banana slicer review below).
Banana slicer review
Up until October 2016, Amazon allowed sellers to provide discounts to customer in exchange for customer reviews. ReviewMeta  found that this policy significantly boosted the weight of incentivized reviews to make out the majority of ratings – and tended to be a lot more favorable. In October 2016, Amazon banned these reviews . Today, however, review integrity still remains an issue – according to Fakespot.com (a site the analyzes suspicious reviews on Amazon) 40% of reviews are unreliable* .
Amazon reviews increasingly incentivized … and makes reviews a lot more favorable
Source: ReviewMeta – 7 million review sample .
What Amazon is doing to combat fake reviews
Quality customer reviews are integral to Amazon’s business model – it is therefore no surprise that Amazon is defending review integrity fiercely:
- Law suits: In 2015-2016, Amazon sued both its own sellers sellers and more than 1,000 individuals for having solicited or provided fake reviews . While helpful as a deterrent, suing all fake reviewers ex post is a quite resource intensive strategy.
- “Verified Purchase”: Reviewers who Amazon can track in the system to have actually bought a product have a “verified purchase” tagged to their reviews. This will deter sellers from soliciting reviews, or at least so for high ticket items. Recently, sellers have found a way around: an elderly Boston couple started receiving countless smaller products from Amazon that they didn’t order — purchased by a seller who used their address to “verify” a purchase and earn the right to review .
- “X# people found helpful”: Customers can up/downvote reviews that are found precise and helpful.
- AI screen: Finally, Amazon uses AI to detect precise and trustworthy reviews and give them a preferential weight and placement .
* The site only analyses reviews reported by customers, which would most likely bias the result upwards.
 https://techcrunch.com/2016/10/27/amazon-sues-more-sellers-for-buying-fake-reviews/ and https://gizmodo.com/amazon-starts-suing-its-own-sellers-in-latest-fight-aga-1780043360