There are no good independent measurements of market share between the various distributions of desktop Linux, and that is leading to a continued back-and-forth between rivals.
In the latest installment, Fedora leader Max Spevack takes a shot at Ubuntu leader Mark Shuttleworth, who last year estimated Ubuntu's distribution at eight million users and, recently, re-estimated that down to about six million:
I have a follow up question, Mr. Shuttleworth. How did you manage to lose about 2 million users in less than 10 months? What does that mean for the future of Canonical and the funding that you provide to Ubuntu? Or were your numbers then, and now, simply made up? How many users do you actually have? Your inconsistent tales to reporters detract from the good work that the Ubuntu community guys like Jono and others are doing.
Spevack then points to this statistics page and says the Fedora community "makes a good-faith attempt at statistical transparency." The numbers seem to indicate that anywhere from 65,000 to 177,000 unique visitors a week download Fedora.
Ubuntu has been on somewhat of a roll this year, including an agreement by Dell, Round Rock, Texas, to pre-load the flavor of Linux on some of its notebooks and desktops. But, to date, there have been no independently certified numbers on Ubuntu's installed base.