Supposedly you can earn "5x anywhere" by using credit cards to pay for prepaid or reloadable cards at the right merchants. But what about registering for conferences or other online purchases where they want a billing address? These are non-recurring purchases, mind you. I just got turned down for one such purchase using a Visa prepaid debit card, on the grounds I didn't have a billing address for that card. Any workarounds? Or are these 1x purchases no matter what? P.S. Maybe I can use my Bluebird funded by debit prepaids to pay for these expenditures, but Amex isn't always honored. And I can use my BB to pay off my credit card bills, so I'm not really gaining anything by using it to pay merchants and conference organizers.