Prior to the invention of the light bulb, people slept an average of 10 hours a night. Today, the average American sleeps less than seven hours per night, a decline of 25% since the early 1990s, according to Facts, Figures & the Future, a service of ACNielsen. As a result, sleep has become a multi-billion dollar industry, with about 42 million sleeping pill prescriptions filled last year, up nearly 60% from 2000. Meanwhile, advertising for sleep products exceeded $300 million in 2006 and is...