Mobile advertising platform AdMob has released its Mobile Metrics Report looking at statistics for the month of March. It highlights some interesting trends in smartphone applications.

AdMob serves ads for over 6,000 web sites and 1,000 apps and stores and analyzes the data from each ad request, impression, and click. The report is intended to provide insight into trends in the mobile ecosystem.

Growth in requests from devices running the Android and iPhone Operating Systems (OS) continued to outpace other platforms in March, despite the relatively limited number of devices in market, AdMob says.

Over half of Android and iPhone requests came from apps. In the first five months following the launch of the Android Market in the US (November 2008 to March 2009), Android requests increased an average of 47% per month. In the first five months following the launch of the App Store in the US (July 2008 to November 2008), requests from the iPhone increased an average of 88 percent per month. Here’s a look at Android vs. iPhone requests:

Other noteworthy findings from AdMob include:

- The HTC Dream (G1) generated 72 million requests, giving it 2% share of the overall US Market in March.

- In the US in March, the HTC Dream (G1) was the number 10 overall device and the number 4 smartphone, after the iPhone, BlackBerry Curve, and BlackBerry Pearl.

- The Android OS now has 6% of the US smartphone market and is tied with Palm as the fourth-largest OS.

- The iPhone generated 8 times more US requests than Android in March. The iPhone platform in total (iPhone and iPod touch) worldwide generated 23 times more requests than Android.

Android/iPhone comparison is based on requests for AdMob ads on the mobile web and in apps from the G1 and iPhone in the USW. AdMob’s full report can be viewed here (pdf).