Capital One
Someone very close to me was just scammed by Capital One. He made a purchase for (rounding) $100, and used the Capital One card. He was denied, initially. Ok, whatever, so he uses another card and goes home. Now it seems that Capital One DID CHARGE HIM, and wasn't going to give the money to the vendor! If you have a Capital One card, DO NOT USE IT. If you do, and this happens, call them out on it, and give them hell!