"As everyone who ever tried it knows that trying to
count how many people use a particular Linux distribution is almost
impossible. Now, Rick Lehrbaum, founder of LinuxDevices and a
friend and former editor of mine, has tried a new and interesting
way to count Linux users on his new site, LinuxTrends: look at
Google search results for the various Linux distributions.
"Some of the results aren't surprising. Ubuntu has become far
more popular than the other mainstream distributions of 2004/2005:
SUSE Linux, Fedora, Debian and Mandrake/Mandriva.
"Still, these distributions' decline to the Ubuntu juggernaut is
nothing like as bad as the fall in popularity seen by the
second-tier distributions of 2004/2005. Of Slackware, Gentoo, Arch
and CentOS, only CentOS, a RHEL (Red Hat Enterprise Linux) clone,
has retained much of its popularity."