^^^^^^^^^^^^^^Most of the Linux computers sold in the Far East are reformatted by customers with pirated copies of Windows.^^^^^^^^^^^^^
#2 by userbase, not by marketshare.
By apple's own numbers, they have roughly 25 million users.
Gartner projected linux to pass the mac this year(05) as #2 as well as IDC, who thought it more likely to have happened in 2003.
Apple is losing userbase to linux as well. Doesn't have to be much, but right off the top of my head I can think of a person who uses a mac, linux only. Linus Torvalds. It'd be plain stupidity to think he's the only one.
Mac is #3.
For U.S. retail store computer sales in September, Apple was reported to have a 6.7% marketshare - a big jump over previous reports. Gartner and IDC missed that prediction. Perhaps the figures you saw excluded OS products pre-installed on new computers?
I use Linux for servers, and it does a great job at that. But the Linux user interface is awful for the average desktop/laptop computer user. Frankly, it's stinks worse than Windows.
BusinessWeek is publishing an article tomorrow - November 10, 2005 - Apple's Growing Army of Converts - reporting that an increasing number of computer users are dumping Windows and switching to Macs.
Yellow Dog Linux. Quite popular. It'll even run an XServe faster than OS X. OTOH, don't forget that probably most current Linux uses are for servers, not desktops. Linux is definitely ahead of Apple in servers.
Linux also has an infinitesimally small marketshare of joe user, much higher only in the geek world.