The other aspect of television that is changing is the advertising nature of television is changing much like newspapers, the old model doesn’t translate well to multiple technology driven vehicles for delivering content.
The programming and viewing habits of the last 50 years — exemplified by the checkerboard of competing programs on the broadcast networks — are being replaced by an Internet-influenced time-shifting model of scheduling. As a result, the very definition of prime time may be changing
[From Jay Leno’s Move Hints at Future of Prime-Time TV - NYTimes.com]