This isn't exactly news and belongs on reddit under one of their conspiracy forums.. Amazon has quite a few number of people working to stop this type of stuff. If you want to help I'd shoot them this link.

Some people may be 'product testers', take a look at the person "Mystic Reviewers". She is a real person, her pics in her reviews match her facebook page. She works at a reputation management company in San Fran and only has done 5 star reviews.

@gonzi I think your comments are a bit cynical. I don't think this sort of stuff is common knowledge. If it is true that there is a ring of sellers, this is really highly coordinated, dare I say almost organized ecommerce crime. I for one, certainly would like to know these sellers get away with it. I think it is appropriate to get Hacker News community to weigh in on how it might be achieved.