Great line from their FAQ:

    Q. Can a Coin be used to skim cards?
    A. No. You can only add cards that you own to your Coin.

Ummmm... I hate to be pedantic [1], but the question is using the "is it possible" meaning of "can", but the answer seems to be using the "am I allowed to" meaning. There's a line in the previous question about how "As an additional safeguard, the Coin app will only allow you to add cards you own," but no detail on the mechanism of this magical authentication process.

[1] Who am I kidding? I love being pedantic.