I'll never understand why people at work leave their computers on all the time, just to save a minute or two booting up in the morning. It doesn't make sense to me to leave them running about four times longer than necessary, doing absolutely nothing except for burning through hundreds of watts every hour and shortening their usable life.
Fair enough, if you're computer's downloading stuff or encoding DVD rips overnight or whatever, that's different. Or if it's a server, of course... But these ones just do nothing at all. And there must be millions like that around the country.