If you put your own memory card into a kiosk to get newspapers or books, what are the chances you could spread a virus that way? I know Linux is fairly virus-resistant, but the kiosk maker might decide to go with some flavor of Windows, which seems to be a virus magnet. And people tend to put the memory cards/sticks into PCs, too.
I'm not sure about putting the identification on the memory card. Publishers will assume that someone will try to copy it and give it away, so they may try to put some bogus DRM on the card itself or something.
Then if you lose that card, you lose your whole subscription.