Android has surged ahead of Apple for the first time as the most popular smartphone OS, according to Millennial Media's mobile ad network.
In Millennial Media's December report, Google's mobile operating system won 46 percent of all ad impressions (the number of times an ad is displayed), compared with 32 percent for Apple's iOS. In November, the two operating systems were neck and neck at 38 percent each.
Rounding up the rest of the competition, Research In Motion's BlackBerry OS grabbed 16 percent of ad impressions in December, Nokia's Symbian nabbed 2 percent, and Microsoft's Windows Mobile snagged 1 percent.
Looking separately at mobile device makers, Apple accounted for 3 of the top 30 devices, with its iPhone, iPod Touch, and iPad. The iPhone, not surprisingly, ranked No. 1 among the 30 devices. Collectively, Apple's three devices accounted for 21 percent of all ad impressions on mobile devices on the network.
Samsung as a whole ranked in second place behind Apple for the largest number of ad impressions thanks to its solid lineup of Android phones. And the company's Window-based Samsung Code managed to squeeze in enough ad impressions to make it the only Windows Mobile device to make it into Millennial Media's top 30. Overall, Samsung was credited with 17 percent of all ad impressions and 7 of the top 30 devices.
In third place was HTC with 15 percent share of all ad impressions and 9 devices--the highest number of any manufacturer. RIM took fourth place with 12 percent and 5 devices. Of note, RIM's BlackBerry Curve was No. 2--behind the iPhone.
Overall, smartphones continued to rise in popularity compared with feature phones, accounting for 23 of the top 30 devices last month and winning a combined 48 percent share of all ad impressions.
Looking ahead, Millennial Media's sees not only Android but also RIM and Windows Phone 7 applying pressure on Apple's iOS this year. But one question the blog doesn't address is how the upcoming Verizon iPhone might upset the mobile apple cart and impact the fight between Android and Apple for ad impressions and market share. According to Millennial Media, its ad network reaches 85 percent of U.S. mobile Web users.