I agree. The fundemental decision need to some from "the top". The example I like to give is that when I am in my source
 editor, I dont want my harddrive to power down, even if I stare dumbly at my code editor for more than two minutes.  

I think power managment system need a notion of task state from which power configurations are derived.   

There is quite a bit of stuff published on the topic. I'm still plowing though it. I 've yet to find a scheme that 
really appeals to me. However, none of them are based on the idea that low-level devices autonomously turn themselves 
off. 

-ad