The increased complexity of TV shows is sometimes offered as evidence of an increasing sophisticated audience who has come to appreciate greater complexity in their entertainment. Look at shows like Lost and The Sopranos with their ambiguity and their multiple, interweaving plot lines and so on. Presumably, the implication seems to be, people have adapted to the conventions of television and require greater amount of complexity to hold their now-mammoth capacity for attention, for holding complicated details suspended in their minds.
But this argument, as flattering as it is to us and despite how pleasant its justification of our couch-potatodom may be, doesn't seem quite right. The shows aren't more complex so much as they eschew unnecessary reiteration of what is going on and what the conflicts and tensions are supposed to be. In reminiscing with a friend about Twin Peaks we recalled how the integrity of the show was compromised by the efforts it had to make to bring in and acclimate new viewers who arrived at the show late -- perhaps after the avalanche of hype that greeted its first few episodes. New shows don't confront that problem. Writers and producers don't have to worry about incorporating inane exposition (like you see on daily soaps -- the convention that most makes them seem sort of dense to non-viewers) or introducing new plot lines to hook new viewers. They know that when people hear hype, they will start from the beginning, not tune in in medias res. The writers can therefore plot accordingly, comfortable in the knowledge that new and potentially confused viewers can (a) see episodes on demand or during one of HBO's frequent re-runs, (b) catch up online, (c) rent the DVDs, which come out almost immediately after a season first airs, or (d) download episodes from pirate sites. Considering (c), it almost behooves producers to insist on a certain complexity that would require viewers to pony up for the DVDs.
So 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. So lamentably, Twin Peaks was ahead of its time in this sense; if it were being made now, there probably wouldn't have ever been that awful Miss Twin Peaks side plot.