Economic doubts cast cloud over fall TV season

US broadcast networks head into the fall television season armed with more than three dozen new shows and billions of dollars in advertising commitments -- but a few wicked plot twists may still be in store.

Ahead of the 2010-2011 TV season, ABC, CBS, NBC and Fox have sold about $8.2 billion in advance commercial time, up around 17 percent from last year, with higher prices and sales volume. But analysts caution that the confidence advertisers showed in early sales could be slipping, and prices could come under pressure if the broadcast networks failed to deliver a few breakout hits, or if worries about the economy deepened. "We've seen big increases in TV ad pricing and inventory sold, but the question is if it's sustainable," said Tony Wible, analyst with Janney Capital Markets.