I guess the idea is that if FB has your card details it'll be a bit like Facebook Connect and will lower transaction friction. Which is exactly what Paypal does. Except - and it's quite incredible really - as a purchaser I'd trust Paypal much more than I trust Facebook, I don't want my purchase history being sold along with all my other personal data thankyou.

The idea of trusting something less than Paypal is amazing, go Facebook!