A chart from Millenial Media provides the data, erm, on the data, for the US at least. This shows the share of mobile advertising impressions, not handset share, from November 2011.
While it’s no surprise to see Android with the largest share, it is surprising that it is only 50% and that RIM manages a respectable 17% given their relatively limited browser.
Part of this is explained by the fact the data includes tablet share, with Apple still heavily dominant in this market, although the recent launch of the Kindle Fire Android tablet will address this balance.
Indeed, normally secretive Amazon proudly announced Kindle Fire sales of 1m devices a week making a statement about their intent and ability to gain decent tablet market share.