A new survey reveals that the median age for TV audiences is at a record high of 51, higher than the national median age.  This is actually bad news for the networks because it means that the average TV viewer is actually older than advertisers' target demographic.  That's not entirely surprising since younger people have been abandoning network TV in growing numbers in the past decade.  The growth of video and game rentals shows that younger Americans are no longer willing to set their lives to the networks' schedule by becoming involved with episodic TV.  Perfect examples of this trend are American Idol, whose audience has wged from 36 to 44 over the last seven seasons, and Dancing With the Stars, whose median audience age is 60.