I've just read an article about Amazon suing reviewers for hire on Fiverr.com. It can be tempting to go that path when it only costs a fiver to hire someone to post a review when you are struggling to get some reviews on your ebook.
Don't do it. Amazon will pull your paid positive reviews and may unlist your book and you can't do a thing about it.
These Fiverr reviewers don't even write the review. You are asked to provide a review for them to post. This starts to make all reviews suspect and people will start to disregard reviews.
Amazon doesn't want that to happen as a certain percentage of books sold are because of the number of positive reviews that book has.
Amazon is the biggest book market on the web so keep anything you do on the web: keep it clean and keep it legal.
However, the big boys in publishing have been providing free books for reviews for a very long time.
The question is will Amazon dare remove any reviews from authors the big boys represent?
Here's the link to the article: