Seriously, where do people get these numbers? My thing about this is this. We know many small companies don't pay for their software HERE in the states (one of my biggest challenges as a small biz IT consultant/freelancer). We also know that Chinese piracy is considered an art form in some places. Taken together, the market share statement makes little sense. How can you know what the share is, if you've no legit data?
One other thing, to someone who NEVER USED a computer and just want web, email, and simple things like YouTube or word processing(most people don't use even a tenth the total capabilities of Word or Excel). They will see nothing special about Windows, Linux, Solaris, FreeBSD as they all can do that with no real issue.
Let me preface this with, I'm writing this on my Ubuntu powered notebook, that's authed against my 2008 AD that also auths my kid's Gallery running on another Linux server.
Most people will cry, "But those other OSes have hardware issues please help us", and I'll whisper, "No." .... and then remember that these machines came with Linux and thus should already work fine since it's 2009 and not 1999.