My best guess is that if your card is already registered with a Coin account, it then cannot be registered with another Coin account. And if that is the case you are probably more secure owning a Coin then you would be if you didn’t own a Coin

The Brooks Review

Gee, it would be a pity if someone skimmed your card, huh? Better buy our product. It’ll protect you against… other users of our product.