The itunes check would only work for a card you use for itunes it would seem.
On the contrary, the iTunes account check seems to be an important piece of validation security for registering a new card.
iTunes allows an immediate comparison of, at the very least, the name of the person registering the card versus the name on the card. It'd be pretty unlikely that the bank will automatically let someone with an iTunes account name and credit card on file for John Doe, register a random card from Sue Thomas.
You left this out which is the most important part: (snip)
Apple has stated repeatedly that they do not store the full account numbers themselves. I did not think it needed to be restated.
Moreover, it's certainly not the most important part.
Especially since the first card that most people will likely register for Apple Pay, is their default iTunes one that's already stored WITH ITS FULL ACCOUNT NUMBER in Apple iTunes servers.
Either you already trust their servers or you don't.
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Which brings up this point: token purchases cannot guarantee the account number's security, if we
ever use that same card number for any non-tokenized purchases. A chain is only as strong as its weakest link.
In other words, if account number security is really that important to someone, they should dedicate one card to Apple Pay and NEVER use that same card number in the clear in any other way, online or in person.
As previously posted, I already do something similar with my cards. I use one card only in person. One card only for online purchases. And one card only for recurring payments. That way, having one number compromised does not affect the others.