Michael Mace of Mobile Opportunity has posted an interesting article called "Does anybody really know what smartphone market share is?"
The first surprise is that Nielsen shows Apple in fourth place in smartphone share. That's wildly different from what Canalys, the source usually reported, has been saying (link).
Canalys shows Apple's market share as 28% in Q3 2007 while Nielsen shows it at 8% at the same time.
The conflict in the numbers underlines how ridiculously useless the publicly-available third party sales numbers are in the mobile phone market, and how little attention the press is paying to the inconsistencies. Apple's share varies from 8% to 28%, and no one even notices. Hey, we got a pretty chart and it confirms what we wanted to say, so don't ask questions.
Speaking of pretty charts, did anyone notice the one shown in Steve Jobs' keynote earlier this year? Take a look at it again. The graphic was actually designed to make Apple's pie piece look bigger. Also missing is the fact that Windows Mobile (because Microsoft is not a manufacturer) actually takes up a chunk of the Palm, Motorola, and "Other" pie pieces.
However, in that same Canalys report, you'll also see some more-useful OS-based market share percentages: In Q4 2007, Canalys estimates that Symbian had a 65% share of worldwide converged device shipments, ahead of Microsoft on 12% and RIM on 11%.
So it seems that whether you're a Blackberry, Windows Mobile, Symbian, or iPhone fan, you can probably find some market share figures that show your Mobile OS choice is more popular than others. And hey, what's stopping you from making up your own figures?