Each month, AdMob, a mobile advertising network, rounds up the data from over 6,000 mobile web sites and applications, analyzes it all, and releases their findings in their Mobile Metrics Report . In the September report , AdMob determined that the iPhone had become the #4 handset worldwide by count of ads requested. In the October release, the iPhone has skyrocketed all the way to #1. Note that these rankings are not directly representative of sales numbers; while AdMob's ad network is wide enough that these numbers can provide an accurate picture of usage trends, they don't necessarily prove that one handset is outselling another.