I was thinking of something more like in the desert where the distance becomes a haze. Here is some examples:

http://www.gamespot.com/gamecube/driving...ag=images;img;1

Nintendo uses this in most of their games. Take a look at the distance in the screenshots, it's slightly blurred. Basically the farther away from the camera, the more blurry the world becomes. I don't think it's DOF as everything near the camera, no matter where, stays clear(no focal point ect.). And I don't think the blur depends on the objects origin compared to the camera either, as the ground becomes blurred in the distance too.