AdMob has released its May Mobile Metrics report today, outlining the rapid growth of smartphones over the past two years. The mobile ad network also noted that while smartphones have been quick to penetrate the global market, there’s still some disparities across regions, for the distribution of devices used to access the Internet.

For this year’s report, AdMob revisited the mobile themes of the past two years. The primary data centered around ad requests on networks and devices. From the Mobile Metrics report, we can see the growth of mobile ad requests, doubling to 46% worldwide. The iPhone and iPod Touch combined brought less than 2% of worldwide ad requests in May 2008, but now Apple and Google’s Android dominate nearly half the global market.

Some key points from AdMob:

• Smartphones accounted for 46 percent of traffic, feature phones for 42 percent of traffic and Mobile Internet Devices for 12 percent of traffic in May 2010.
• Motorola feature phones were the top three devices in AdMob’s network in May 2008, but in May 2010 the only Motorola device in the top ten was the Droid.
• The Nokia N70 was the number one smartphone in AdMob’s network in May 2008. It dropped to number two in May 2009 and down to number four in May 2010, but continues to be the top smartphone from Nokia in AdMob’s network.
• The Top 5 iPad countries in AdMob’s network, based on the number of unique devices, were the United States (58 percent), Japan (5 percent), United Kingdom (4 percent), China (4 percent), and Canada (3 percent).

comScore confirms much of what AdMob has seen in terms of global growth for smartphones, noting the rising demand in Europe for Apple and Android devices. Aside from lowered prices, the innovation around these platforms has come in the way of mobile apps. They’ve helped drive the demand and success of smartphones, becoming central to their respective platform’s monetization.

Looking forward, that means mobile apps are necessary for sustaining the marketplace around platforms and devices. Considering the interest around mobile Flash and HTML5, it’s easy to see how important related display ads will be on mobile devices in the near future. Maintaining control over the platform’s marketplace is key towards its monetization, which is probably why RIM is looking for more control with its stock buyback.

In addition to flashy display ads, mobile app developers will also need to look at ways to cross-network, particularly on each major platform. As consumer behavior orients itself around the handy smartphone, apps will need to tap into each other in order to create the level of personalized advertising that will be the only effective route years down the line.