Imagine if you're playing, say, blackjack with a human dealer. After you win a hand but before you collect your winnings, you ask the dealer, "Say, would you mind if I retroactively increase my bet and collect the winnings on that?" The dealer replies, "Sure thing," and pays you accordingly.
I imagine we'd all agree that there's no harm in asking, and that the dealer's compliance is his own problem and a problem for his employer but not your problem. Why does this suddenly change when you're talking to a computer instead of a human? I'm not saying it doesn't change, but I can't entirely figure out why we approach these two scenarios so differently.
For your ATM comparison, it's not uncommon for excessively-clever bank customers to jokingly ask the teller for a million bucks, often in response to a question like, "Is there anything else I can do for you today?" Suppose you found a particularly dim teller who decided to actually hand over a million bucks when you asked. We'd blame the teller and the bank for agreeing to such a thing, not the person who asked, right? Yet when it's an ATM instead of a teller, we blame the person asking.