A report done by Angus Crawford for the BBC has found that a much 20% of on-line reviews are fake. He tracked down a student in Bangladesh who says he posts reviews on web sites for money and Crawford quoted many examples of writers on the web offering review-writing services to companies. This is a big issue for theatres, hotels, holidays etc where a number of bad reviews can kill their business for most of the year or the duration of a show, and in severe cases, permanently.
This issue is probably less prevalent in the book world as a bad review is often a sign that the book was the wrong choice or wrong genre for the reader, and a host of five star reviews doesn’t mean it will appeal to everyone. In any case, an author has the option of re-editing their book, or writing another to win back lost readers, a much more difficult process to go through in theatre, film and hotels. A few years ago, Amazon had to clamp down on authors reviewing their own books and posting bad reviews of others, such as RJ Ellory, under an assumed name, praising his own book, A Quiet belief in Angels and bad mouthing Dark Blood by Stuart McBride. I don’t know if much of this goes on in book circles and I guess we’ll never know, but if you hear of anything, please let me know.