At the resort I worked at, it was widely known for years that the "top instructors" on the private board would offer $10 kick backs to the girls at the desk selling privates in order to get the private requests.
Guess I've got my head in the sand. I've never heard of this. I would never think of doing it. I would hope no one I work with (sales or instructors) would do it. Flat out unethical.