Google's Android operating system broke a two-month statistical tie with Apple's iOS in ad impressions in a big way in December, grabbing 46 percent of hits.
Millennial Media had Android and iOS tied for 38 percent of ad impression share in November, with each platform commanding a 37 percent share through October.
"For the first time, we saw Android surpass iOS as the largest smartphone operating system on our network last month, with an 8 percent month-over-month increase and 46 percent of the impression share," according to Millennial, the largest free-standing mobile ad network. "iOS represented 32 percent of the impression share."
RIM's BlackBerry OS grabbed 16 percent share of impressions, while Microsoft Windows Mobile devices secured a paltry 2 percent of impressions.
Millennial also found that Android had collected 55 percent of ad revenue through December, compared to 39 percent for iOS. Overall, ad requests from Android phones to Millennial's network grew more than 3,000 percent in 2010.
The new figures come one week after comScore said Android handsets passed iOS handsets in the U.S.
While Android may have trounced iOS and all comers in ad impressions, the iPhone is still top dog for Millennial.
The ad network said Apple remained the leading device manufacturer on its network, grabbing 21 percent of the top 15 manufacturers' impression share in December.
The iPhone also overwhelmingly led Millennial's list of top 30 devices, with a 12.5 percent share. Next was the BlackBerry Curve with 6.5 percent.
Apple's iPod touch, the HTC Nexus One, aka HTC Passion, was No. 4. The Motorola Droid nabbed the fifth spot. Android devices comprised 16 of Millennial's Top 30 Mobile Devices in December.
That figure is up from 11 devices in November, proof that while Apple clearly has the most popular smartphone in the United States, Android poses strength in numbers.
Millennial expects new Android, Windows Phone 7 and RIM OS handsets to continue to pressure iOS in 2011.
Then again, maybe not so much, with the CMDA (Code Division Multiple Access )-based iPhone 4 hitting the Verizon Wireless' network February 10.
With analysts expecting Verizon to sell anywhere from 9 million to 15 million iPhone 4 units, Millennial will see many more iOS ad impressions in 2011.
It will be worth paying close attention to Millennial's March numbers when they're released in April. The March numbers will include one full month of ads-served figures on iOS with the new Verizon iPhone.