Originally Posted by MG23
Nobody even knows how many Linux desktops exist, because there are no sales figures to count. I have multiple Linux desktop machines at work and we have a Linux desktop at home, a Linux laptop, a Linux server and a Linux netbook... I doubt any of them are reporting statistics to anyone. Occasionally I boot the laptop into Windows to edit video or play a game that doesn't run on Linux, but otherwise I don't miss it.
And the desktop market itself has peaked; there'll be desktop computers for a long time to come, but the big growth is likely to be in various kinds of mobile hardware. Linux has a substantial presence in the mobile market while Windows has hardly any; I've seen iPhones and Android phones but I've never ever seen a Windows phone.
Figures given for PC OS marketshare are usually based on useragent data from people visiting the Akamai top 500 or something like that, I think.
Must call you out on your phone statement - looking at the diagram linked to by Mike Bracknell, only Android is linux-based. Symbian uses a proprietary kernel and iOS uses the Darwin kernel, which as you probably well know is a derivative of a derivative of Unix, but not Linux.