Funny, one of the companies I was contracting with last summer got so wrapped up in this craze, they devoted an entire room to walking desks. You could go in there when you wanted and work. They have 8 treadmills rigged with a desktop so you could plug in your laptop and mouse and work while you were walking.

Never saw more than two or three people in there at a time, but the company made a big deal out of it. It looked pretty awkward, even when people were walking really slow.