why are there so many of these things? (off-topic)

In The Daily today:

The latest mind-bending show to explore the question of how we know what's real, NBC's "Awake" tells the story of LAPD homicide detective Michael Brittan, a man who has no ability or desire to distinguish between his actual life and his extremely detailed dreams.
Dual-Reality TV by Noam S. Cohen The Daily | Wednesday February 29, 2012

Battlestar Galactica, Invasion, American Horror Story, The 4400, V, Source Code, Haven (right?) .... even the theme song to Friday Night Lights, for pete's sake.

There've been so many of these stories that new shows with the same premise aren't new any more but merely "the latest" variant. Characters who are dead and don't know it, or they're aliens and don't know it, or they're pregnant with aliens and don't know it, or they're asleep (or awake) and don't know it -- the possibilities are endless.

I date this meme to 9/11, but I don't know whether that's right.