Everyone's looking to crucify the ATC on duty when we don't know how much time he was working prior to this shift, if he had rest, etc. Pilots and truckers etc are mandated x hours of rest in the y hours preceding their shifts. Do ATCs have the same stipulation?
Everyone knows that an air traffic controller's job is one of the highest-stress occupations there is. If there have been cutbacks in staffing (and it's hard to assume there hasn't been, in this day and age), could this guy have been on the butt end of a double-overtime shift, or have had such a tour prior to this incident?
All of my argument presumes this was an accidental nodding off. If it wasn't and in fact he was deliberately dozing on duty (as I think I heard about recently at another site, where some guy actually brought bedding with him into the cab) then all bets are off.