I'm not sure what to make of these statistics. Virtually every web site I visit is running on Linux, some flavour of BSD, or Solaris. I've only encountered one that uses IIS - Microsoft.com itself.
I really don't blame them, either. The Windows system arcitecture is totally unsuitable for running a long term server. It may have protected memory, but it still has the old shared address system problems. Windows users might be lucky to run some weeks without downtime. Linux users regularly report uptime in the years. Add to this that Linux is extremely powerful and open-source, meaning you can make whatever fixes or modifications that suit you. (Insert usual Linux vs Windows blah here, but you know it makes sense.) I know that if I ever needed to set up a router or a server, Windows wouldn't even be an option.
The only advantage Windows has is that its easier to use. Linux is not a system for ease of use and never will be. But apart from that, a company would have to be crazy to opt for Windows - unless "coerced" by Microsoft. I guess you all know M$'s tactics by now.