Mobile Advertising company Millennial Media has more evidence of Android's growing strength. For the first time, Google's platform has surpassed Apple's iOS as the top operating system on Millennial's mobile ad network.

Android nabbed 46 percent of the impression share for December, compared to Apple's 32 percent. That's an eight percent month-to-month increase for Android and a 12 percent decrease for Apple. BlackBerry maker RIM fell into third place with 16 percent of the impression share, down three percent from November.

"In 2011, we anticipate that we'll continue to see increased platform diversity with not only Android, but RIM and Windows Phone 7 applying pressure on iOS," Mack McKelvey, Millennial Media's senior vice president of marketing, said in a blog post. "This prediction once again stresses the importance of advertising and developing across platforms."

Requests for Android ads grew by 141 percent from the third to fourth quarter, and in the past year Android has seen a 3130 percent increase on the Millennial network. In contrast, Apple had just 12 percent quarter-to-quarter growth, and since January of 2010, iOS ad requests saw a 14 percent uptick.

There could be a number of reasons for this lopsided growth. Google's Android is still a relatively new platform, with the first phone running the OS launching in fall 2008. Apple started selling the iPhone in summer 2007. Google also has more experience in the advertising realm because its revenue model is closely tied to ads with systems like Google Ad Words.

On top of that, Apple's iOS is limited to a handful of products, while there is a wealth of options for Android-based devices.

Android is also divvied out across many different carriers, while Apple's iPhone has been exclusive with AT&T. But will 2011 bring new growth for iOS? On Tuesday it was announced that Verizon had landed the iPhone and will start supporting the device in February. There are reports that suggest more carriers will soonget the iPhone, too.

Android greatly strengthened its foothold in the mobile market last year. New data from comScore said that Android leapfrogged iOS to become the number two operating system in the U.S. But it's a close race. Google's platform has 26 percent of the market in its grip while Apple is behind by a hair with 25 percent. BlackBerry is still king with a 33.5 percent piece of the mobile platform pie.