1st Place in Derby #313: College!, with 225 votes!
It was customary in firing squads for one of the guns to hold a blank cartridge instead of a live round. This was meant to free the members of the squad from the guilt of execution, as individuals never knew whether they had fired a live or blank round.
Perhaps the Galactic Empire got this backwards and gave all but one of their troopers blank blaster rounds. In this case, it's not the troopers who should be blamed for their incredibly ineffective gunfire, but the Imperial bureaucrat who filed the blaster paperwork.
Of course, that would mean that there is one trooper out there with a live round, just waiting for some rebel scum to cross his path. All the snide jokes about trooper accuracy will be laid to rest when this guy mows down a hoard of escaping do-gooders.