I question the morality of the for free demand. Why the owner cannot pay the regular fee, and therefore maintain his independence? I have been offered free session in exchange of a review in my blog and I have not accepted. If I take the free token, then I will feel obliged to reattribute with a positive review. I prefer to pay and keep therefore my ability to not publish a review if I did not find the experience satisfactory.
Asking a session for free is, in my opinion, abusive.
It has also happened to me that certain professionals have ended in my sack without a contract. In these cases they never asked for a review.