None. Bill Gates will just redefine Darkness® as the industry standard.
or
Because he wanted sweet dreams.
or
Three. One to climb the ladder while the second kicks the ladder out from under her. And the third to say, "I knew that was too high for you dear."
or
6: 2 to screw in the bulb and 4 to testify that it was lit from the moment they began screwing.
or