In fact, it seems like it might be worth investing in 2 or 3 monitors anyway... screen space is cheap and might make you more productive?

Here's a small (and probably cherry-picked) collection of studies, which I haven't examined closely, but which seem to agree with my subjective impression: ~50% productivity improvement on tasks involving multiple large simultaneously-relevant windows and tight interaction loops (data analysis, in my case), less but still substantial benefit on programming.

It seems like it'd be obviously worth investing a couple hundred dollars in a second monitor for anyone who wants to do this.

Maybe I am nosier than the average person, but if Vladimir's desktop were constantly in my field of vision, Will, I would spend too much time looking at it. I hide my Viewer window after verifying that Vladimir is not procrastinating. Then I set a timer to remind me to look at the Viewer window again in 5 or 10 minutes.

If Vladimir and I had founded a start-up together or I was paying him $8000 a month to work for me, then more likely than not I would prefer for his desktop to be constantly in my field of vision, but the way it is now I do not have that much of a stake in his performance at the keyboard.