I often wonder why the lights are left on all night in office buildings in America. It seems like a colossal waste of energy. The cost should be offset by more intelligent detection and control systems, which have many uses beyond simple energy savings, as demonstrated here by Wroclaw University of Technology students in Poland:

Dorm Becomes Huge Light Display

Instead of fireworks displays, which are so 17th century, the cities could come alive with annual building light shows. Buildings could also give emergency messages, or be used to indicate temperature and weather change. The energy being burned every hour of every night could be put to so many more uses. The technology is ready: