My anecdotal evidence from the startup world, though, says that most people in a "startup" like Facebook work very hard and very long hours at the same time. I think your description is a very good way to work, but I sort of doubt that this is an accurate description of life at Facebook :P
My info is anecdotal from my wife, who has spent a significant portion of her life working with bears. But from the zoo keepers I've met, that mammal breakdown is true for most of the felines and primates as well.