I was thinking of installed base (48% in the U.S. in August, compared to 23% for iOS, source http://searchengineland.com/comscore-android-nears-50-us-sma... ) and applications, but revenue is (or was late last year) part of the picture, too, via advertising:
Google CEO Eric Schmidt says Android-based phones already generate enough new advertising revenue to cover the cost of the software’s development.
