True. But it would work with all of your personal cards, which is the main proliferation problem. You could use them together. Get a Wallaby as your "one" smar

True. But it would work with all of your personal cards, which is the main proliferation problem. You could use them together. Get a Wallaby as your "one" smart personal card, and if you feel like springing $100 to go from 2 cards down to 1, you've got Coin. Personally I'd be a tad worried about handing my Coin to a server to charge a big business meal. What if they accidentally tap the button and switch to my personal card when they're holding it?