A consumer research group surveyed Amazon and found significant evidence suggesting fake reviews for many items. Since reviews often influence your search results and help you decide, the fake reviews are potentially leading customers to bogus products.
Excerpt: "One example, a set of headphones by an unknown brand called Celebrat, had 439 reviews, all of which were five-star, unverified and were posted on the same day, suggesting they had been automated."
In addition to fake review, Amazon is known for offering fake products.