Is this really news??
Most positive product review are sappy BS about the product being the best thing since sliced bread or the internet, with very little insightful commentary. That leads me to believe they're always fake. I consider product reviews a form of advertising. And since most consumers, who are already easily influenced (such as by TV commercials and other mass advertising) won't bother looking for articles about fake reviews, the fake reviews will do their job, and convince people to buy the product.
If you really want to find out about a product, you can dig through all the BS to find a review with insightful commentary (and then do some cross reference to verify the claims), but that can be difficult. I find it more helpful to read all the negative reviews of a seller or product. If the negative reviews don't paint a horrible picture, you can use them to weigh the product's or service's faults against its claimed benefits.