(Disclaimer: I work in advertising. I get paid to notice these things.

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Honestly, reality shows, as the "big trend" in network TV, peaked 3 or 4 years ago. Then, the networks' schedules were full of them, because they were cheap to make, and got good ratings. Now, there's only a handful left (Survivor, Amazing Race, American Idol, Dancing with the Stars, maybe one or two more)...though, if you expand the argument to cable, there's more, obviously. And I, for one, say, "thank gawd"...I found nearly all the reality shows to be uninteresting at best, tawdry at worst.
As with all things on TV, trends change. The huge popularity of series like CSI, 24, and Lost has swung the pendulum, and now you see an awful lot of "procedurals" (CSI / Law & Order and their spawn) and "unraveling mystery" shows...all of which are scripted, hour-long dramas.