Advertising and Statistics
There is certainly a prerequisite for statistics we can’t get around: data. Online advertising services generate tons of it; most not accessible for the public and many probably not very interesting at all.
Chitika has made one statistics public for us: the penetration of iPhones on the AT&T and Verizon network
We don’t get any info on how the data is measured (iPhone versions, representative placement of ads, …) and (unfortunately) there is no historic data, i.e., a time series.
Nonetheless, verizon is catching up quite fast, and I bet the CEOs of competitor networks in other countries Apple finally opened up, would die to get these figures for their networks …