AFAIK, Paxum explicitly stated that it was not MasterCard who caused the trouble.
Please verify, and if it proves wrong, rename this thread. It's not nice to spread wrong accusations about others, be it a person or a company.
It would be banks. I doubt any sane exchange would take credit cards, the story should be "Bitcoiners won't accept disputable, reversible, high fee payments, or reward companies that extract fees from person-to-person commerce." If you have a merchant account, you know very well that processing a credit card payment is being given money that you hope doesn't get yanked out of your account months later, with a $25 fee to do the paperwork of disputing the chargeback when it happens. Too many disputes, and the merchant services will start demanding a minimum 10%-20%+ of your transactions held for months.