[MayanAstronaut]

Much like search engines combat black hat SEO, amazon and reviews systems can do the same.

It would not be to hard too for amazon. Use reviews that are a 'Verified Purchase' and highly 'helpful' reviews as a training/test set. Then machine learn a weighting to every review based on the (product, reviewer, other reviews, etc features...)

The outcome could actually hinder tactics like this for products that game the system much like how link farms hurt sites they were propping up when Google figured out how to stop sites from gaming a search engine.

[tracker1]

In this case, the positive fake reviews are for verified purchases of ebooks that are relatively cheap... I'd suggest reviews from accounts more than 2 years old, with over 5 reviews, and more than $500 spent would probably be a better baseline for training.

[echoless]

It's always a cat and mouse game however. Once they employ machine learning, I'm assuming the spammers will adapt and create reviews that fool the algorithm(though at an increased initial cost).

[notatoad]

Trusting "verified purchase" reviews is a pretty easy way to allow a lot of fake reviews. On a 99c ebook your royalty is 35%, that means a verified fake review only costs you 65c.