I'm in the UK, so we are/were already using pin and chip cards, and it was a barclays card with chip and pin that I scanned with my nexus 7... as said a simple nfc app read 'important' details from my card. IIRC there is a £30 allowance for payments without using my pin and it 'should' ask for a pin after several in a row but if you do just one transaction per person walking down the street, say in London, that soon adds up. All it takes is the right tool/software, like in the olden days with card skimmers. We already have apps like paypal which can access pin and chip readers on your phone, we have payment from phones so using that as a basis for the coding of the software isn't outside the realms of possibility.