I started writing reviews on Amazon some eight years ago. I have done 235 at this point, not a massive number, but reasonable. I generally write reviews of books, professional ones, not novels, and always do so in my own name. I generally discount anonymous reviews, especially ones with less than rational name tags. I also use the reviews to see what may be wrong with a product. What breaks, what is poorly designed. Many negative reviews are just folks with a chip on their shoulder but who cares.
Now reviews have value and when Amazon decided to change their format I decided to follow the comments of those feeling I thought in a right minded manner. I am not a trained Psychiatrist but I can at times fell the chill of reading some of these comments. They appear to be folks who have no other life, who take minutia quite seriously and can be overly aggressive about small issues. Perhaps DHS and NSA should be watching these discussion groups.
Are Reviews useful? I believe so. If they are honest and present positive and negative factors then they can help the consumer. Frankly if I know who the Reviewer is then I have mush more reliance on the Review. But it appears that Amazon may have an out of control process here. There are people writing thousands of reviews by getting tons of free stuff. The IRS aside, how can anyone do a credible review of so many items? It may take me a couple of weeks at least to prepare a book review. And then only if I have the time!
Thus this Review process has many flaws. Especially the anonymous elements and in addition the element of what appears to be "gift" reviews. Add to that what seems to be less than well balanced folks, well, you can see where that leads.
I have seen over the years that if you give a book a credible but bad review, the Collective which may form around the writer, such as those in the Net Neutrality space, go mad and drive your review away. A key to detecting that is a bimodal set of Reviews, five and one star, with may positive on the five and many negative on the one. That is an example of the Collective at work.