In reply to ShamusR.

My bet is that it is just saved in case there is a dispute on the charge. There is nothing to compare to unless they made you get your card out of your wallet. In other cases, I think merchants are trying to get address/ phone number information but with Passbook loyalty card capabilities, they have a great avenue for that. Panera has a great app for ordering online, Walgreens integrates their BalanceRewards card, including clipped coupons on your phone. I've never used coupons but now do at Walgreens.