??
Here is another example: We were in a Safeway store in Pacifica (California) a couple months ago. When we checked out, our Capital One Visa card was declined. What a surprise! This card has a fairly high 5 figure limit and has always been paid in full each month. No problem, I simply pulled out a Citi MasterCard... it too was declined. Panic was starting to set in as many scenarios rumbled around in my mind -- visions of drained accounts and such. Okay, lets try American Express. That was accepted. (The total was around $80, BTW)
A couple hours later, I received a phone call from Capital One asking to confirm my last three charges. (This is a common occurrence since we travel quite a bit and my purchases have no logical explanation -- in their opinion.) Anyway, this Safeway charge was among the questionable transactions. I told the operator that one was not authorized. She said there was no problem since it had been declined by the bank. When I asked why, she explained that particular Safeway store was one of those in which (alleged) employees had attached a device that captures CC data. Apparently, AMEX was just not up to speed.
Anyway, having multiple cards would not have changed things but it did give piece of mind that at least we still had access to funds... at least, for that moment.