re: Apple's Mobile Commerce Future: AuthenTec Just The Start
Well, let's examine the real world. I have to fish my credit/debit card out of my wallet/purse, swipe it through a card reader which may or may not read it correctly the first time (repeat as necessary) and type a PIN or try and sign my name on a low-res touch pad with a stylus the size of an extra-large crayon. Hardly seems like less effort than pulling out my phone (which, most people are probably heavily engaged with before the reach the counter), tap my finger and select a single icon on the home screen (correction to your comment, there would be no going to the App Store, I'm assuming the purchases would all be done within Passport, i.e. in app).
Maybe something as trivial as the coffee shop isn't the best example, but Passport does seem like a great option for things like movie/concert tickets, restaurant checks, hotel bills, taxi fares, etc.