I come from a factory background where it wasn't uncommon to spend the entire 8-12 hours working at the fastest safe pace I could. After a year of developing, I still spend almost no time on water-cooler talk and web browsing, the only things that are clearly not work. I don't see anybody else wasting time like that either. I wonder if the 'barely four hours a day' people would not count stuff like editing a wiki, investigtating a log, and so forth.

My job isn't 100% programming by any stretch. But when I do have programming, I spend 8 hours straight. It doesn't seem to make me very productive, but I do spend it all hard at work.