In my experience since the store swipes the card to activate it and also they scan the barcode in the back to ring it up. It is possible that the person who rung them in did not activate them by swiping each one but you would think that would be one of the first things a cashier is taught because they are a pain to do. I think that if they were not all activated that would be the cashiers fault but why would one have worked and 2 not work? In my experience it takes a few mins or more to activate them and you get a reciept of each card that would have told me something was wrong if I had not gotten them because it also on the receipt says activated and a little bit of the barcode of the card. Our credit card and gift card area also have a sign that says credit cards and gift cards are worthless without being activated for those who steal them thinking they are getting free gift cards.