Hi people,
Just to let you know that I saw a programme on morning television this morning (Philip Scofield was discussing it with a group of people) and they said that many people who sell stuff on Amazon are paying for reviews via Fiver.
This doesn't mean just author/book reviews.  They said that there's a difference between selling price between a book or selling a holiday that the reviewer has not been on.
If they find out that this is happening, whatever the reviewer is reviewing, then they are going to sue.  Probably the person selling the product that's been reviewed.
They said that the way to tell if it's a genuine review is the following:
Professional/paid for reviewers are short and to the point and non-emotive and that they provide just a paragraph of hte benefits.  
Whereas, the 'general public' who review are very verbose and personal - expressing emotions about their 'feelings' on the product, rather than just how the product will benefit the potential purchaser..
They think this is the way they can tell whether a professional has been paid to review a product/book and hasn't actually read it, as opposed to a person who has actively engaged with it.  
Also, professional reviewers post many, many reviews on various products.  Sometimes several in one day.
Just some hints and tips for you.
Kaye 

My first defence against rogue online reviews is to treat all of them individually with a large pinch of salt. If a product or service only has a few reviews, and they are all either 1-star or 5-star (or whatever the extremes are), I dismiss them as being from rivals or friends of the seller, respectively. Only when there are a reasonably large number, and they cover a broad range of scores, do I begin taking them seriously.

The other thing to be wary of is a product or service where all of the reviews are recent, whereas the seller is claiming to have been in business for a longer period. For example, earlier this year, I was looking for a tradesman to revamp my bathroom. I found a website which claimed only to represent reliable tradesmen who all had references from happy customers. The problem was, I noticed that several of the tradesmen I was interested in claimed to have been in business for several years, and to have lots of happy customers willing to provide references; yet all of the references shown on the site were within the previous 3 months. Coincidence? I don't think so. I think the respective tradesmen had paid friends to write reviews. I decided not to trust those reviews, or those tradesmen.

I think it's wise to treat any kind of online advice, including reviews, in the same way you would treat advice from a random bloke in the pub.