I’ve had this happen to me. I brought the ATM card into the branch (fortunately it was business hours) and gave it to a teller.
I would try to return the card, and failing that, destroy it. But first I would probably make a balance inquiry because I’m a really curious person.
This actually happened to me; I walked up to the ATM machine and it was flashing the message “Do you wish to make another transaction?” There was no one around; I pressed ‘no’, put the card in my pocket and took it to the bank the following morning; I gave it to the branch manager and that was that.
Oh, I voted that I would take nothing.
I’d try to use it repeatedly with 1111 as the security code to get the machine to keep it so I don’t have to return it.
As a side note, they are using new machines in my area that make the user take the card back before continuing on with the transaction.
Well, there’s also the possibility that you know the guy, and think that he’s a jerk who deserves to lose his money. It is possible to steal while thinking you are doing right. But I doubt the courts will be amused by someone claiming they were playing Robin Hood via ATM.
Of course I wouldn’t steal. It’s both wrong and stupid; you’d get caught. There’s a camera, and by the time you realize there’s a card in there, the camera has seen you. And god knows I’ve lost cards before, and never had anything stolen. I ought to pay that forward.
I didn’t vote on whether to return it; I might return it, especially during bank hours and if the ATM is attached to a bank. If the ATM was in the middle of something non-bank-like, I might take it home and cut it up. It’s a hassle for the person to get a new card, but they’ll be happy that no one stole anything, mostly.
I did this once. First, I considered running after the woman who had just left it, but I had been waiting and I didn’t want to lose my place in line. So after I finished my transaction, I took it to the bank (which was just across the street, so no big deal, I thought). Where I was grilled about who I was, and where I found it, and what time I found it.
Next time, I’ll just take it home and shred it.
I wouldn’t take any money. If the ATM weren’t attached to the bank, I’d ring the bank with a view to returning the card or at lest to advise them that the card had been lost and was now in my possession.
I’d take nothing and try to return it. I had a credit card fall out of my pocket onto the sidewalk once and someone found it and mailed it back to me. Another time, my brother lost my cell phone on a public bus and someone turned it into the driver and the central office went through the address book and called me to let me know they had it. Neither time was anything stolen from me. So I figure I owe some strangers.
This exact thing happened to me. I went to the ATM and instead of “Insert your card” it said “How much do you want?” So without thinking I said “hur hur hur” to myself and hit the maximum allowable amount button. The money came out, but then the card came out too, and the situation changed immediately from me having fun with a technical fault and free money, to me stealing from an individual. I felt terrible and went straight into the bank and handed over the card and money, and lied to them, saying that the money was in the tray when I arrived at the ATM.
Ten years ago most of the ATMs around here didn’t have cameras (according to a bank employee I knew at the time). That may have changed. Regardless, I’m not a thief and I wouldn’t steal from someone. I would take the card out and see if there was some way I could drop it into the deposit box if the bank wasn’t open or nearby. If I couldn’t do that, I’d call them and report it, or drop it in to the police station on my way home.
At least one person would always know.
So, nobody would make a deposit? Wouldn’t it be kind of cool (if you had the $$) to deposit twenty dollars just to mess with the card’s owner?
I turned in $1 that was left in the change dispenser of the self-checkout at my local grocery last week, so I’d turn in the card and full amount of the cash.
I was in line behind a car at a drive-up ATM a few years ago and the car in front of me left their card in the machine. Once I realized it, the other car was gone. I took the card to the bank the next day. It’s what I would want someone to do for me.
I wouldn’t even think twice. I wouldn’t take a dime and would find some way to return that card.
Now that’d be funny. 
The card owner desperately checks their account after they realize their card is gone, and… more money is in there than expected?
Bank of America has an incredibly annoying (but in hindsight, safe) policy that any time you try to start a new transaction (which includes pressing the back button) at an ATM, you must re-enter your PIN. This is to protect people who run away from the ATM the moment their cash is spit out, without ending the transaction or taking their card. So really, the only way this would ever happen at my bank is if somebody types in their PIN and then walks away immediately.
I hear that an incredibly common scam in NYC for people who find lost ATM cards is to take them to the nearest subway station and buy a couple of $80 metrocards (the machine won’t ask you for a PIN or signature if you charge it as credit rather than debit), and then start reselling swipes at the station for $1 a piece (swipes cost $2.25 the honest way). This way, by the time the ATM’s owner realizes that they lost the card, and call the bank, and then the bank reverses the metrocard purchase, and thus the card gets flagged, the scammer has already made a good $50.
I’m very pleased with the honest and law-abiding denizens of the SDMB, and can also categorically state I wouldn’t take anything and would try and return the card, based on the ethic of reciprocity.
I’ll admit I’d be tempted, but I would try to return the card without taking any money.
I came across a machine with both the card and the money there.
I looked around to see where the owner was, I could have easily walked away with both, I was about to take it out and put it through the letterbox, fortunately the owner rushed back.