With my xbox i had an idle shutdown of 1 hour, so if i was watching a movie at night and i fall asleep an hour after the movie completed the xbox would shutdown.
Now I use my PS3 for my media (Only because my xbox is to noisy) but I fall asleep sometimes and wake up to see my PS3 still on and I get annoyed that such an advanced machine doesn't realise that nobody is using it and shutdown. this may be a fault of my own because i haven't found an option that may exist.
But then again my six-axis stays on aswell which is silly, even the Wii controllers shutdown after 10 minutes on non use.