Linux desktop market share: Small no matter how you measure
It doesn't give me any pleasure in saying this, but the evidence is overwhelming that Linux is not huge on the desktop. Saying it has maybe 1% of the desktop marketshare is probably not realistic, but not as far off the mark as we'd like.
Measuring Linux market share is not an easy task, especially not on the desktop. Most Linux users don't buy Linux pre-loaded, they download Ubuntu, Fedora, Debian, openSUSE, or another distro from a series of mirrors, BitTorrents, or share CDs. No matter how you count up, though, the total number is pretty small compared to the number of desktops in use.
A lot of folks are bandying about a 1% figure, citing Web statistics and so on. Caitlyn Martin, over on O'Reilly Broadcast, says that the 1% figure is a myth, and goes on to argue that "Educated guesswork probably puts Linux at close to 10%, just about even with MacOS. That is a far cry from 1% and is in no way insignificant."