I use my dad's credit card all of the time. Instead of my using my card and then my dad reimbursing me by going to the bank to deposit money from his account, I just swipe his card. Especially when I go to the grocery or go run errands for him. I don't see why if I have the last name as him, I can't sign my OWN name and be fine. I've never had a problem with any store denying my signature to his card. Many stores have said to sign my OWN name, not my dad's - which I've always done. If I went to a store to purchase something, and got stopped, I would be really upset. I understand that it's for the card owner's security, but PLEASE! He's my FATHER who gave me PERMISSION to use it.