Google's (NASDAQ:GOOG) Android operating system accounted for 53 percent of advertising impressions in the second quarter, according to Millennial Media's latest report.
Millennial, the largest freestanding mobile ad network, said Apple's iOS posted a 27 percent share of impressions, growing 4 percent from Q2 2010. Millennial expects Apple to gain share next quarter with the launch of the iPhone 5 in the third quarter.
Of course, one might argue Android could pad its lead with the launch of the Samsung Galaxy S II handset this summer. Samsung is holding a media event August 29 to introduce the highly-anticipated handset, which is thinner, lighter and faster than its predecessors.
Overall, smartphones led the network's smartphone, feature phone and connected device mix with 67 percent of impressions. Connected devices, which includes tablets, MP3 players, gaming consoles and electronic readers, saw a 13 percent jump from Q2 2010 and accounted for 17 percent of the ad impression mix.
Millennial also celebrated its 50 mobile ad report since March 2009, and there have been some drastic changes since then. The major constant is that Apple's iPhone remains the top smartphone by impressions.
In March 2009, the iPhone represented 5.82 percent of ad impressions on Millennial's network. Today, that number has tripled to 16.2 percent.
No surprise there; Apple has sold over 100 million iPhones worldwide since 2007, and its withstood the onslaught of Android handsets more than admirably.
Moreover, Apple ranked as the third largest smartphone maker on Millennial with 11 percent share in its first study. The company has gained 20 percentage points to command a 30 percent share at the top of the heap.
Speaking of Android smartphones, you can find exactly one on Millennial's network in March 2009: T-Mobile's now much-dated G1.
Today, two thirds of Millennial's top smartphones comprise Android handsets. The Motorola Droid is the top Droid with 2.95 percent of impressions, while the Samsung Nexus S wields a respectable 2.71 percent share.
Those Android phones follow the only two smartphones that remain from Millennial's first list of the top 20 phones in March 2009: the popular iPhone at No. 1 and the resilient BlackBerry Curve from Research in Motion at No. 2.