Caitlyn Martin of O'Reilly Broadcast has another interesting article about why the figure of Linux market share is quite a bit more than the oft-quoted 1%. She starts out by doing a bit of math: (1 Linux netbook)/(3 total netbooks) * (18 total netbooks)/(100 (desktops + laptops + netbooks)) = (6 Linux netbooks)/(100 (desktops + laptops + netbooks)) — Linux netbook sales alone constitute 6% of the total desktop market. I can't argue with that. It's also a really impressive number; the number for total Linux desktop sales (that includes desktops, laptops, and netbooks) will obviously be higher — I don't know by how much, but the total number is certainly at least 6%. I think it's great that Linux desktop sales have come this far.
The bigger question regards the meaning of this number, and I believe the problems with this article occur before and after the calculations. For one, the author starts by saying that Linux market share in servers and embedded systems is significant. I don't think anyone ever doubted this, and several studies have shown that Linux distributions are in fact in the majority on these types of hardware. Therefore, I think it isn't quite right to start the article like this when the title clearly indicates a discussion about Linux desktop market share. That said, this is a fairly minor issue.
The article's argument gets more murky when Steve Ballmer is brought into the discussion. It has been written repeatedly that the presentation referenced clearly shows that the biggest threat to Microsoft Windows is illegally copied versions of Microsoft Windows (not Linux, Mac OS X, or BSD). Why? This is the case in many countries with poorer populations, as people simply can't afford to buy a licensed copy of Microsoft Windows. Furthermore, Linux adoption in these countries is low because the computers sold there often don't have the tools (Internet connection, working USB port, working disk writer drive) to create a live CD/USB, and there's no cost advantage to using Linux as people will just copy Microsoft Windows. A lot of commenters in the linked article also point out that in these countries where unlicensed use of Microsoft Windows is rampant, it is cheaper, in fact, to buy a machine with Linux preinstalled and then wipe the hard drive and install an unlicensed copy of Microsoft Windows. I don't doubt the verity of this. That said, the 6% figure is for the US, where unlicensed Microsoft Windows use is likely to be much lower; therein lies another problem, as statistics for US Linux market share is being compared to statistics for worldwide Microsoft Windows market share.
And why should Steve Ballmer know about precise statistics for Linux and Mac OS X usage? It certainly is easy to look at sales statistics and see what percentage of computers are sold with licensed copies of Microsoft Windows; also, as Microsoft "phones home" to see which copies of Windows are licensed and which are not, it should be pretty easy to tell how many unlicensed copies of Windows are being used. While one can safely conclude that the rest of the pie is occupied by Linux, BSD, and Mac OS X, it is not so clear how much each contender has of that slice of the pie. I guess one way of telling how many people use Mac OS X is by tracking sales of Microsoft Office for Mac, but this is problematic as many Mac OS X users stay away from Microsoft Office and instead use iWork, OpenOffice.org/NeoOffice, or a web-based productivity suite.
So why would Steve Ballmer put Linux market share at or above Mac OS X market share? Microsoft knows that it can compete with Apple's Mac OS X in terms of features (in some ways) and price, so Mac OS X isn't really considered a huge threat. On the other hand, Linux can do most of the things a typical computer user wants (e.g. web browsing, productivity, peripheral support) for free, which does technically pose a serious threat to Microsoft Windows. At the same time, Microsoft has repeatedly accused the free software community (and Linux in particular) of infringing upon its patents. Therefore, Microsoft is pegging Linux market share that high in order to justify those accusations — if Linux market share is that high, then of course Linux needs to be stopped before such patent infringement gets out of control! (This is what I would imagine a Microsoft executive saying at such a presentation.)
I won't argue that Linux desktop sales make up at least 6% of total desktop sales. Usage is a different matter entirely and should not be treated the same as sales figures.