[tass]

This is fairly anecdotal, but I've read some people's experiences with free products for reviews. They received products while they were giving good reviews. The products stopped once a bad review was posted.

Amazon also gives free products for review (Amazon Vine) but these are made very clear with a banner above the review, and will remain part of the program so long as they continue to receive a high number of 'helpful' votes on their reviews.