iPhone and Android again reign supreme in AdMob’s most recent metrics for May released today. AdMob took occasion to look back at its past two years of data with this most recent report and found that iPhone and Android have accounted for a lot of the growth in the mobile Web.

According to the report, in May 2008, the iPhone and iPod touch generated 1.3 percent of worldwide requests and the first Android handset was still six months from launching. Two years later, the two platforms accounted for 42 percent of all ad requests worldwide, driven by strong application usage. 

Smartphones in general have done quite well. In May 2008, they generated 22 percent of ad requests and in May 2010, smartphones accounted for 46 percent of ad requests. Feature phones accounted for 42 percent of traffic and mobile Internet devices for 12 percent of traffic in May 2010.

To give some perspective on how big smartphones have become worldwide: Motorola feature phones took the top three devices worldwide in AdMob’s network in May 2008. Today the iPhone is the top device with 18.8 percent of ad requests, followed by the iPod touch (11 percent). The Motorola Droid was a distant third globally, with just 3 percent of ad requests globally.

Regardless of what device people are using to access the mobile Web, the report found that they’re doing it a lot more in recent times. Traffic from North America, Asia, Western Europe, Latin America and Oceania all increased by a factor of at least six times from May 2008 to May 2010.

AdMob, which was recently acquired by Google, serves ads for more than 23,000 mobile websites and applications around the world. AdMob stores and analyzes the data from every ad request, impression and click and uses this to optimize ad matching in its network. The company’s monthly report offers a snapshot of its data to provide insight into trends in the mobile ecosystem.