If you call the bank and are even able to convince them that you're, let's say Nilay Patel, it's not like they're going to repeat your own social security number back to you, because that's information they'd expect you'd already have. If it were really that easy, all you'd have to do is call different big banks with names of various people you know exist. Odds are most people have at least one card with a big bank like Chase, Citi, B of A, etc. But it's not that easy though. Try it with Nilay. What identity information that you'll need to steal his identity are you able to find with Google?