Washington Mutual ATMs (and I'm sure those of other banks are similar), when sitting unused, have a sort of screen saver mode with a slideshow of advertisements for the bank. When you start using it, it shifts to showing screens that accept your input. But when you trigger an action that takes more than a moment to complete, such as delivering cash to you or preparing to accept your deposit envelope, the screen goes back to its screen saver mode until this preparation is complete.

I find this behavior pretty unappealing from a user interface perspective. I want to feel like the machine is paying attention to me for the duration of my usage, not going back to twiddling its thumbs whenever it stops interacting with me for more than a second. But more importantly, it sometimes seems that this interface is designed to make people forget to take their bank cards with them when they leave. This is because one of the actions that triggers the screen saver mode is when the ATM has been told that you don't want anything else from it, and is preparing to give you back your card and (optionally) your receipt. Thus the situation in which you're about to get your card back is momentarily indistinguishable from the situation that the ATM is totally done serving you. I've witnessed several people forget their cards, and done it myself once, as a result of this terrible interface design.

This would of course be moot if the ATM hardware allowed you to 'dip' your card rather than surrendering it to the machine for the duration of the transaction.