Authors are often banned from leaving reviews on sites such as Amazon. They consider it competition. But many authors are actually avid readers and know a good book when they read it. Also the author world is extremely small and we tend to know one another. We know the new authors and the great ones.
Non-author/average readers often obtain books directly from an author or publisher as a gift or as a member of a fan club. Amazon frowns on reviews from such readers.
Amazon is trying to do the right thing and make certain that all their reviews are from legitimate purchases and are not prejudiced in any way. They are attempting to make sure that the reviews posted are not from the author, the author’s mother, or best friend. Obviously this site cannot prevent that.
What this site can do is open the door for anyone to post a review of an e-book that they have read. It is meant only for the best of the best. This is for the books that stand out as a cut above the average, the cream of the crop.