In Linux/BSD/Unix, it depends more on the window manager (dwm/wmii/ion3/ratpoison/etc nullify the need of 2nd monitor)

I guess the 2 monitor programmers are windows guys (nothing wrong with that) ... and then they migrate to osx/linux, bringing the bad habits and polluting osx/linux over time

your second monitor for MBP, is it used for extending the view for osx, or it's just a cloned view of the laptop screen (let's say via external monitor cable)?

if it's a cloned view, vnc is an old and reliable technique that works regardless of cpu/os used (you can control powerpc mac, intel mac, windows, linux, bsd machines ... in one box)

dual/multi-boot and parallel guys, try to beat that! :D