This still confuses me. Perhaps because Windows is so behind when it comes to this, but wouldn't Virtual Desktops be more efficient in at least two ways:
1) In terms of electricity use
2) Keeping eyes focused on one screen
Most UNIX-y systems have had this type of system since the 80's. Windows has yet to implement it, but there are third-party add-ons to support it. OSX has had 'Spaces' since 10.5
I personally use XFCE on Gentoo Linux. I have 8 virtual desktops configured on my desktop at home and work, and 6 on my laptop. It supports up to 100. XFCE offers an option to switch virtual desktops by dragging your mouse to the edge of the screen. It even offers a threshold on how hard you try to push to the next screen. I keep mine lax because I'm used to it, and very rarely accidentally switch to the next virtual desktop. Alternative methods are using the Pager or the scroll wheel on the desktop.
As stated, outside of Multi-seat setups (that Windows does not support) I still fail to see any purpose to having more than one physical screen in an office or home environment.