Beds on an Airplane

I spent quite a bit of time on an airplane this last week and the one though I kept having was "I need a bed".  From my eyeballing calculations it looks like if you arranged the beds bunk style you could get just as many people in the plane.  You could keep planes with seats for the day flights and run bed planes on red-eye and over seas flight.  I would gladly exchange my cramped sitting position for a cramped sleeping position, heck you could even take some of my square inches away and I would still be happy as long as I could lie down.