Fake reviews plague consumer websites | Money | The Guardian
This is an interesting article by The Guardian - some of the follow-up comments are quite funny, too.
I can point to a number of reviews on Bloviation's TP page that are good candidates for being "adverts" rather than reviews. There was even one which was worded in terms of "what we want you to say" rather than "what I experienced". (Which now appears to have been reworded to reflect the first-person experience rather than a provided template, although not particularly imaginatively).
Paul..