Well - I carry 3, and would carry 7 if I wasn't trying to slim down my wallet. Those 3 are: * An personal AMEX cashback card, that gives me a very nice 5% bac

Well - I carry 3, and would carry 7 if I wasn't trying to slim down my wallet. Those 3 are: * An personal AMEX cashback card, that gives me a very nice 5% back in certain categories, and 1% back on everything else. * A Visa Airline miles card, for places that don't take AMEX or travel spending where I earn 2x or more miles. * A business Visa credit card for the business my wife owns. The other cards I'd carry if I wasn't annoyed by a thick wallet are: * A Costco AMEX that gives me extra cashback at Costco. * A couple store-specific Visa cards that give me nice benefits at stores where I shop at least semi-regularly. * A work credit card for my work. I'm a bit of a miles/cashback junkie, but I'll bet many people have at least a few cards they'd like to consolodate. The average American family has 8. Like I said in another comment, I'd be thrilled if I could replace all those with one card, and I'd be happy to pay what Plastc is asking if it worked. But the most likely scenario I see for that happening is mobile payments a'la ApplePay.