this is probably not what you mean, but as you mentioned "video" and "background":
one thing i really hate is how the media player automatically pauses a video as soon as you ctrl+backspace to another task. that's trying to be smart. i can manually pause a video if i want to. usually though, switching away from a running clip without pausing it means i want to answer an sms or refresh the web page that shows my trains current delay... it's like turning around for more beer when you're watching tv at home. you don't want the show to pause for these 3 seconds. you still follow the dialogs while you refill your glass.... and you wouldn't look away in the middle of an action-packed scene that requires full attention, anyway. so why cant i read an incoming message while at least the audio of my clip still plays on?

i don't want to start a discussion on this particular "feature" (already happened elsewhere). it's just an example: don't let such things become too "smart". they usually get in the way then.