> Mythbusters, I rarely come out of watching that show feeling like I really learned something

The earliest episodes were more scientific and educational. They spent quite a bit of time explaining how they were going to construct something and then showing how they actually built it. It became pure entertainment--devoted especially to blowing things up--once the show achieved success.

Another example of a show descending to the lowest common denominator: The first years of "Biography" on the A&E Network had stories about explorers, scientists, and world leaders--Michelangelo, Henry Ford, Julius Caesar, Marconi, Marco Polo--but now it's nothing but celebrities.