This is Josh, CTO of card.io. Those are definitely challenges, but we've put quite a lot of effort into handling exactly those sorts of problems, and we do pret

This is Josh, CTO of card.io. Those are definitely challenges, but we've put quite a lot of effort into handling exactly those sorts of problems, and we do pretty well with them (if I say so myself). One interesting tidbit on this front, from someone who spends a lot of time admiring credit cards: Only some cards have silvery ink on top of the numbers. Some others have silvery plastic underneath the main ink layer (usually part of the card's overall graphic design), so the numbers become more silvery with wear, not less. And yet others have no silver anywhere at all. TAANSTAFL. :)