Third as many as for a regular bulb.
Two. One to arrest the room for being black, and the other to arrest the bulb for being broke.
Just one, but it takes a really long time, and the lightbulb has to want to change...
How many libertarians does it take to screw in a light-bulb? None. The market will take care of it.
One, but it takes at least three light bulbs.
