Amazon authors are vulnerable to the following fraud, that would eventually result in significant business loss for Amazon.
A start-up company selling good reviews for $500 per book with a $100 monthly fee. It would work as follows.
A new book receives several negative reviews (1-star) using the methodology developed in the previous section
The author is then reached by email: typically, most authors have a public email address easy to harvest with automated tools, or easy to purchase from mailing list re-sellers
The start-up offers to post good reviews only (and it does not discuss the bad reviews previously planted before reaching out to the author to "fix" the problem)
How scalable is this? A college student could easily make $500 a day, targeting only a few books each day. That's $100k per year, and collect the money via Paypal. Because the money is relatively easy to make, a large number of (educated and under-employed) people could be interested in setting up such a scheme, eventually targeting thousands of authors each day when combined together. Or someone might find a way to automate this activity, maybe using a Botnet, and make millions of dollars each year. Many authors would eventually refuse to have their books listed on Amazon, and choose to self-publish with platforms such as Lulu. Publishers would also opt out of Amazon. Revenue on Amazon (from book sales) would drop. Or Amazon could simply eliminate all reviews and not accept new ones.
Interestingly, it appears that Yelp might be making money with a similar scheme: out of fake reviews and blackmailing small businesses listed on its website. And I've seen companies selling fake Twitter followers or Facebook profiles, though they quickly disappear. Even LinkedIn was recently victim of a massive scheme involving fake profiles automatically generated.