I worked on the customer review team at Amazon once upon a time. There are definitely fake reviews, and Amazon is well aware of "review rings" where people trade reviews, vote each other's reviews up, etc. Much like Google, they stop some and allow others, because the more feedback you give scammers in general, the better they can adapt.
In short: fake reviews and fake review upvotes very much exist and are WAY more rampant than you'd ever believe. It's an 80/20 or maybe 90/10 problem - most of the review content on Amazon comes from a small percentage of active users, and as soon as you become active on the site you start to get sucked into this sort of thing.
In short: fake reviews and fake review upvotes very much exist and are WAY more rampant than you'd ever believe. It's an 80/20 or maybe 90/10 problem - most of the review content on Amazon comes from a small percentage of active users, and as soon as you become active on the site you start to get sucked into this sort of thing.