There was a major discussion in ScubaBoard about a shop using those techniques. The woman who initiated the thread talked about how she came in to inquire about scuba instruction, and then, over a couple glasses of wine with the owner, decided to buy the full set of gear before class, thinking it was all refundable. She did not finish the first pool session before she decided scuba was not for her, and she was shocked to find none of it was refundable. She was most upset about the rebreather she could not return.
I'm a cynic and I have to admit I didn't see that one coming.