Isn't the "old crusty infrastructure" in this case the credit card itself?

It seems ridiculous to try to kill the credit card with... a credit card.

I wouldn't be surprised if Clinkle, LoopPay, Square, or any of the many startups in this space kills the credit card (and thus Coin) before Coin makes its first delivery in Summer 2014.

I think you're underestimating how entrenched the CC companies are in our society. I agree that they'll eventually be replaced, but I doubt it will be in the next year, let alone the next 5 years.

I think Coin is a nice intermediate step between 10 cards in your wallet, and no wallet at all. Intermediate steps are viable businesses. I think Square is an intermediate step, and they seem to be doing just fine. They're obviously going to be at the forefront of eliminating cards all together, but they knew that credit cards aren't going away anytime soon, and so they leveraged that to get their foot in the door with the merchants.

Square, which is a point-of-sale system? Two other things, which the billions of people who use credit cards every day have never heard of?

What would constitute "killing" the credit card, anyway? Less than 5% of the population using it? I don't see that happening for a good 15 or 20 years at a bare minimum.

Do keep in mind, though, that of the "billions of people" who use credit cards, the number that use cards that can be cloned by reading the magnetic stripe is fast dwindling. Until/unless Coin gets cosy enough with the card associations to the point where they can get some way of cloning chip and pin cards (EMV), they're DOA in a quickly rising list of countries that already covers the majority of the developed world.

And a large part of the point of chip and pin cards is that they're meant to be impossible to clone. E.g. in France it supposedly cut card fraud by about 80% for in-person transactions. So unless Coin can convince them that it will be as secure or more secure than these cards, they're going to be pretty much limited to the US, and increasingly get marginalised in the US too: Most large US banks have announced rollout plans for EMV cards (though many will be chip + signature rather than chip + pin).

If you wouldn't be surprised by that, you must not be frequently surprised.

Absolutely not. The old crusty layer is everything you don't see running in the background. The banks, the payment systems, the clearing houses, the entire system as a whole.