I'm always pleased to read your opinions Buzz, and I know you're a strong advocate of keeping the head still. I agree that this is complementary to the earlier thread on stance Praguetaz - which I didn't want to hijack, but which had got me thinking specifically about stillness.
Depth perception is helped by stereopsis, the way the brain uses the different position of two forward facing eyes (parallax) to estimate the range of a distant object - rangefinder cameras use it for focusing. Animals also use motion parallax to achieve the same thing - think of a bird bobbing its head up and down. Imagine a small red sphere, about 9 inches in circumference, approximately 7 feet off the ground, at a distance of say 22yds. By moving your head you get a better perception of its distance and location.
Just playing Devil's advocate, but should we be moving our heads more?