In much the same category, some years ago a chum sold fishing trips from his website. Payment was by credit card, which (in those days, at least) gave full money-back guarantees.
Some customers would go out on the trip, enjoy a day or two fishing but when they got home they would claim to the credit-card company that the (name your niggle here) details were less than satisfactory. The credit-card company always gave a 100% refund, so Greg had paid-out to the boat's owners, paid for food, beer etc, then got zilch from the customer.
Needless to say, once he got wise to this he would accept only Cash payment, from all customers.
Geoff