We have vending machines with these at my university. I often start swiping my card only to realize I've accidentally "tapped to pay" (according to the reader).

The system is cool, imho. For buying something low price, then you don't need to insert password, and I assume with limited operations during certain time. But for expensive ones, you just put your 4 digit pin. The difference is just the card isn't raped on the device.

Each time you pass the card on a place like that it destroy itself, specially if the clerk doesn't have a good day, they just smash the cards until they can't be read.

I replaced 3 cards in a year before the tap system.