I've trotted out the idea of an "Overton Window" applied to realism before. Lately I've observed and pondered a similar notion with respect to lighting.
We're used to certain lighting idioms. Portraits always have a catchlight in the eyes. Models in "fashion" poses are always lit by somewhere between 2 and one million strobes. Even when a model is shot in natural light, we expect to see the shadows filled by strobes to that weird shallow look (see any Sports Illustrated swimsuit edition), and probably gold reflectors all over the place. It only looks superficially like natural light.
A model shot in truly natural light looks downright odd.
The point about the "Overton Window" though, is that it moves. Obviously model lighting moved from somewhere (fewer lights, if nothing else) to where it is today. What's interesting is that it continues to move. As of this writing, Forever 21 (a chain of clothing stores selling cheap clothes to young women, and women who wish they were young) has some campaign photography shot in what I am thinking of as the Facebook aesthetic. The light appears to be dead on front and center, and the highlights are completely blown out. It looks pretty much like on-camera flash, although it's not quite. Possibly the photographer actually could not place a light there, since his camera sans flash was there.
I don't know if this is going to become a new arrow in the fashion quiver, and I don't know it it's really new. It's still an interesting example of how lighting styles evolve, how the window of what we're willing to accept moves. Just as new political idea may or may not succeed in shifting the original Overton Window, this idiom may or may not move the equivalent window of acceptability here.
It's also a marvelous example of how commercial photography steals from popular mass photography. People see this photo of the their friends every day on facebook, it's familiar. To a "sophisticated" viewer, it's terrible, but that's only because we're stuck in last year's Overton Window Of Lighting.
Who's really the sophisticated one?