No support. Charge backs apply to every other market section so why ban such payment options just for membership upgrades? You can just as easily charge back a paypal payment or for gold or account sales as you can for membership.
Besides, most people don't accept direct paypal payments for gold or account unless the person is really trusted. They use PlayerAuctions. Same concept applies for membership upgrades. Bulk buyers prefer to buy membership cards instead of credit card as those are non reversible.