Apply/clear the object fog to selected materials or objects. In one file I have almost 6000 materials so applying and removing the fog takes ages each time, even though I only need to apply the fog to a handful of materials.
I do see how this would improve the user experience, especially for scenes with a lot of materials.
From BlenderArtists forum entry:
I do see how this would improve the user experience, especially for scenes with a lot of materials.