on this video http://www.youtube.com/watch?v=YX_6l2bmvQI at the 1:30 mark the guy punches the dow down. And its a mere light turning. What process is started? or how will the bread differ if I don't do that? I usually don't and I can't seem to notice a difference..
If you punch down a no-knead loaf, on average, you'll get a more consistent crumb and fewer large holes in the finished loaf.