http://androidandme.com/2010/04/news/admob-android-passes-iphone-in-u-s…
Android now accounts for 46% of U.S. smartphone share, while iPhone OS slid to 39%.
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Two Android devices, the HTC Dream and HTC Magic, collectively represented 96% of Android traffic in September 2009. Seven months later, 11 devices represented 96% of Android traffic in the AdMob network.