Facebook changed it's UI again and cut my wasted Facebook time by at least 30%. I predict ad revenues take a hit.

It's possible, if not likely that enjoyment and therefor increased use and distribution will compensate and the hit won't cause a corporate response to change it back. But, ads definitely took a hit in this redesign.

I seldom look at the bottom right hand column anymore because I of the improved update icons on the top left (where your eyes naturally go first). So, I have browsing efficiency. It's like taking all the keys I hit most often and putting them in one place on a keyboard (see Querty vs. Dvorak).

If I'm not thinking about chatting, I don't go down there. I'm more focused, the experience is improved and ads benefit from a more easily distracted viewer. They especially don't benefit from ad space outside the focus view.