In the 1980s and 90s, NBC was a ratings powerhouse. But when its landmark shows left the air, the network's luck ran out. NBC fell to 4th place in 2004 and has remained largely there ever since. Down 9% from last year, NBC's Fall season has been a disaster. New shows have been cancelled and old shows are languishing. NBC will air the Super Bowl and the Olympics in 2012, but the ratings relief they provide will be short-lived. Can the Comcast front office turn NBC around, or have they bought a $13 billion dollar lemon?