I don't know about you, but I've amassed quite a few plastic cards which I rotate in and out of the wallet.  I hate walking around with a big fat wallet.  I do not appreciate the bulge that it makes, or the fact that it presses up against psiatic nerves and can lead to some serious health problems.  Just to name a few:  I have my drivers license, my check card, credit card, club cards, gas card, Starbucks coffee card, rewards membership card, library card, movie rental card, etc.  And I'm fairly certain there are those of you that try to carry them all in one wallet or your purse.  Hopefully, there is one card that can replace them all.