Paypal is Paypal to Amex. It makes no difference whether you transferred money to yourself, bought something on ebay or topped up a pre-pay card. You have always been able to Paypal cash to yourself to generate Amex spend, but the fees usually didn't make it worthwhile.

I might get one for our nanny, actually. I give her £40+ a week for food, nappys etc all of which could be Visa'd - it would be worth a few thousand miles a year and I wouldn't need to visit the cashpoint so often! Probably link it to my BMI card rather than the Amex, though.