I worry that Visa/Mastercard will use their duopolistic position in credit/debit/etc payment processing to gather more data and spy on consumers. I suspect Visa/Mastercard collects even more valuable data than google or facebook and they've already indicated they want to me more of a technology/ML/AI company.

With data being ever more valuable and a small group near monopolistic companies in position to siphon most of it, it's going to be difficult to lead a private life.