Textures un-load?

Since the last update or two, I've noticed something odd.

Textures, besides taking all kinds of extra time to load, seem to un-load after I look away.

For example, I'm in a store looking at a wall. Finally all the boards load and I see the pictures. Then I spin my camera 180 degrees and look at another wall.

When I look back at the first wall, I have to wait for the textures to load again.

Anyone have any idea what that's about, or is this some new "feature"?