> What's to stop Facebook from going after this exact same space? (snip) [To be fair, they don't currently have all the stored credit card info that Apple does. So that's a big hurdle to starting up.]

Google (Android) is probably more likely right now. Or PayPal. If Google or Facebook were to takeover PayPal, or PayPal (Ebay) were to takeover Square or whoever's huge in mobile payments right now, things might start to get interesting.