How would that be any different than general Internet e-commerce, where there is no landlord forcing everyone to use its services? It wouldn't, and nothing disastrous would happen.
It would be the same as browser based e-commerce: stolen credit card information, fraud transactions, leaks of credit card information due to non existing security
This is exactly what apple tried to prevent (snd is earning a shit ton money with it): manual credit card entry because except the big ones almost no one would be safe
