Rob Horning makes an interesting point:
I would argue that the apparent increase in complexity in TV shows is a consequence of the new technologies in delivering content as opposed to the advancing tastes of the viewing public. Lost, for instance, would be unthinkable without those technologies. The audience would have necessarily dwindled as it went on (because new viewers would be hopelessly confused) or the show would have had to solve many more of its mysteries more expediently, to make space for entry points for latecomers.
The Dish 