[lm28469]

Sounds a lot like "if water is good why is coke bad ?"

Just look at the average desk worker posture and it'll tell you more than half of the story already, it's bad for your back, it's bad for your neck, it's bad for you hips, it's bad for breathing, it's bad for blood circulation, it's bad for lymph circulation, &c.

Then there is the fact that you cannot survive without sleep, if you were to spend another 8 hours in bed you'd likely develop bed sores and all kind of nasty things