If there exists a material connection between the owner and the reviewer which is not disclosed in the review then the FTC considers this to be deceptive advertising. A material connection is defined to be something "that is, important to a consumer's decision to buy or use the product." See here: http://www.business.ftc.gov/documents/bus35-advertising-faqs...

So while you might not consider such a review as fake, my understanding is that the FTC would.