Almost everyone I know that owns a Mac dual boots Windows, uses it in a VM, or doesn't use OSX at all. Macs would not have anywhere near the success they have had without Windows compatibility.
As a counterpoint, I don't know a single Mac owner who dual-boots Windows, and only a handful who use a VM for anything (using something like VirtualBox seems to be limited almost exclusively to devs, not normal users). The Mac users I know (and those I see in coffee shops) seem to mainly run Photoshop, Illustrator, a web browser, Powerpoint or Keynote, and Word or Pages, all on OS X. I'm similar except that I also run iTerm2 and ssh to a Linux box in the cloud for my non-Mac needs. But some kind of data on the broader population of mac owners would be interesting.
With respect: I expect you probably do know a lot of folks who dual-boot Macs, they just don't talk about it. Everybody assumes I'm all Mac, all the time, because of my day job. And I do rarely dual-boot--because I have VMware Fusion and just virtualize my Boot Camp partition.
Most people who want to play games on a Mac will dual boot.
I have no idea, but I do know that at most Windows or .Net developer meetups I've been to half the people there are running windows on Apple laptops.
I'm sure we are not alone in the "Must Run Some Windows Software" requirement. ARM might make that tough.