As far as I know, reviewers get free samples of the product, but have to return the samples. I believe there is legislation in the US to force reviewers to disclose if they were given a free sample and allowed to keep it.
“Has the whole world gone crazy? Am I the only one around here who gives a s**t about the rules? Mark it zero!” -Walter Sobchak
“Yup, you were 9-2 when you slid it in me.” -MT Alex