What I'm trying to get at is the percents (70% windows vs 25% linux) seem very counter intuitive. Microsoft links to another company who provides little to no information about how they are making their claims.
Well, if we're doing the anecdotal thing, then I'll be happy to back up mr. maroon. My current contract is with one of those Fortune 500 companies. I work in server ops, and am very much aware of what we have.
There are a couple of thousand servers, across three DCs, a mix of HPUX, Solaris, and Windows.
Not one Linux server. Maybe there's a few dozen running in VMs on developer's workstations, but even they tend to prefer Solaris, since that's their target, anyway.
At this scale, nobody really cares about the licensing costs of an OS. There's no reason not to buy RedHat, if only to keep the PHBs happy.
OS license costs are a smidgen, a rounding error, damn near nothing compared to the costs associated with standing them up, not to mention development, ongoing operations, etc. I'm pretty sure our storage costs, per month, exceed all the money we've spent on licenses in the last year (if not longer).
I also know of a lot of small businesses which have nothing but Windows. I know of few that have even heard of Linux. I'm talking about every law office, every doctor's office, every real-estate office...well, you get the idea.
I like Linux. I've been running it on servers and desktops of my own for over about fifteen years (since the 1.x kernel). I seldom see it in the field.
Since we're comparing anecdotal evidence, for the past 10 years I've been contracting at all manner of large banks, finance companies, telcos, payment processors, and healthcare. They are overwhelmingly using Linux, and mostly Red Hat, in their data centers now. In the early 2000s it was mostly Solaris on Sparc on the back end, but in the last 10 years it has switched to mostly Linux on x86-64, with a smattering of Solaris 10 to run "legacy" applications.
Of course they also run Windows, but it's only for Exchange, Windows file servers, and Active Directory for desktops.
Your environment running only HPUX, Solaris, and Windows, is far from the norm. Linux is widely supported, and most importantly, cheap, compared to HPUX or Solaris (running on custom hardware like Itanium or Sparc).
From http://www.idc.com/getdoc.jsp?containerId=prUS21703309 I've even more willing to believe that the numbers are BS and are entirely about revenue.