That's fine when the business has large reputational constraints. Quite different when dealing with an actor who might be on the margins. Which would include most non brick and mortar businesses. That is to say if the reputational constraints are extremely dispraportionate than what you are discibing works fine. I.E. the difference in the value of starbucks reputation compared to the value of my reputation. However if the two parties are at all similar, than there exists a risk where if you accuse him of being dishonest, he can turn around and say no it was actually you who was dishonest, he is in a position to inflict equal damage to your reputation as you are to his. Cryptographic proof shows, atleast more clearly, who is in the right.