Furthermore, if you accept the current figures one wonders where all those users went. Perhaps they got tired of changing their browsers and moved to Windows? Spontaneous combustion? Or they simply didn't exist in the first place?
(*) And seriously, what percentage of users would be in that situation? Even taking into consideration that it's not just hotmail but other websites I'm not aware of, is it reasonable to assume that the amount of linux users with browsers reporting a Windows machine is actually higher than those who don't? And not just slightly higher, but 5-10 times higher (to make it up to 5-10% market share).