Really? None of your friends have pictures of cats or their babies or grainy shots of them and four other friends as their profile pictures? Because sometimes it feels like half of mine do.

At that point your requiring about as much effort to authorize the transaction as you would be to enter a card number.

Also not sure how secure that would be , how difficult would it be for a would be attacker to find out who was in the images?

I imagine a reverse image search could be fruitful.