The following reminds me of a quick, clever, scene in actor-comedian Steve Martin's L.A. Story:
Two lines of people, dressed for a night on the town inch towards a bank ATM: standing in one line are those withdrawing cash; the second, polite, also well-dressed muggers who greet their prey at the point of transaction, like cheery actor/waiters saying, "Hi! I'm Todd! I'll be your mugger this evening!"
A group of researchers at Algorithmic Research (ARX), an Israeli security firm, published a paper two weeks ago describing a very serious flaw inherent in most ATMs. Apparently, between the time that you input your PIN and the time that the machine spits out your cash, a dataset containing your PIN and account number is encrypted and decrypted a few times while being routed along the banking network -- and somewhere along that point, it's conceivable that those numbers could be intercepted.