An acquaintance of mine relayed the following experience at an ATM:
He went to the ATM machine, performed a transaction, then walked away from the machine, forgetting his card. The next guy in line pulled the card out, put it back in and pulled out $100 and was never asked to enter the PIN number for the card. The third person found the card and turned it into the bank. My acquaintance complained to the bank, who said, in effect, "yeah, we know about this 'feature' but it's too petty to worry about" and reimbursed the stolen $100.
To clarify, it appears once a card has been used, the PIN successfully entered, and the transaction completed, that the ATM remembers the PIN/authorization and allows the cardholder to subsequently insert the card and complete additional transactions without reauthorization (i.e. entering the PIN) provided (I assume) second card hasn't been used and somehow cleared knowledge of the first card.
I cannot vouch for the reliability of this tale, and I didn't turn up anything specific about this 'feature' in the 15 seconds I spent searching the net.
Does anyone else have experience, knowledge, or information about this that corroborates this tale? I'll keep looking and post anything I find.