Net Applications recently published there results of users by operating system. According to them, 0.81% of computer users use Linux. They say they are not counting servers and embedded systems such as TiVo or cell phones. Net Applications are WAY OFF on their statistics and here is why.
Net Applications gather their information by internet activity to sites they track. They do not track the entire Internet (that would be impossible), so the sites they track may not be of interest to most Linux users. Also, most Linux users are very security aware and 'disguise' their web browsing so that they are anonymous or browsing in another operating system. This could definitely skew Net Applications' results.
Net Applications does admit that Linux is growing quickly. They even show that Linux usage has more then doubled since January 2007. I actually believe that that statistic is very optimistic. Linux is growing quickly and has been for sometime, but I think Apple has had tons of growth as of late, thanks the iPod.
So how many Linux users are out there? Well, W3Schools estimates about 3.4%.
Which I think is closer to the actual market share numbers, though I would guess slightly higher, more towards 4%. Why would I guess that? Because of some of the reasons listed in my argument against Net Applications. With the recent success of Apple, I would estimate their market share slightly higher, about 5-7%. This leaves Microsoft sitting around 89-91%. Now I dare you to tell me that they are not a monopoly? Wal-mart doesn't even come that close in market share in their respective market.
So what are the actual numbers. Well, Microsoft says they have about 1 billion users world wide, which is roughly 1/6th or 17% of the world's population. Mark Shuttleworth of Ubuntu claims 6 million users. Linux counter estimates 29 million Linux users and here is why. If my 4% of market share is accurate, then Linux users should be around 35-40 Million, way more then Net Applications' guess and of course I'm right. :)
If you're into statistics, here are some U.S. censuses results about computer and Internet usage.