How many servers out there are actually Linux based?
A LOT. In fact I would assume more than windows on the global scope.
I've run both platforms extensively...my company used windows exclusively when I started and I was plagued with patches, viruses, hacks, licensing problems, reboots needed. I now only expose Linux servers to the internet and will never go back...they just run.
On occasion I do have to use windows due to proprietary drivers for programs and databases, or when a client requests it, but in those cases I actually prefer to use Abyss Web Server on Windows. It's small, simple, good support, and low overhead.