• by Mark Walsh  @markfwal, October 16, 2009

Apple became the top device maker on Millennial Media's mobile ad network for the first time this year in September -- with a 22.4% share of mobile ad impressions, thanks to the iPhone. Apple's 2.65% gain allowed it to edge out Samsung, whose share was roughly flat from the prior month, at 22%.

Among devices, not surprisingly, the iPhone was also No. 1 in share of impressions -- with 13%, trailed by the BlackBerry Curve (6.4%) and the Samsung Instinct (4.3%). Samsung had six of the top 20 mobile phones in the Millennial network, which it says reaches 51.2 million people, or 79% of the 61.4 million U.S. mobile Web users. (Millennial data doesn't include the iPod touch or other non-Wi-Fi devices.)

Analyst reports this week previewing Apple's upcoming quarterly earnings disclosure indicate that iPhone sales are showing no sign of slowing down. Demand for the iPhone 3G S is outstripping supply worldwide, according to Piper Jaffray's Gene Munster, who estimates that 7.5 million iPhones have been sold in the last quarter.

Highlighting the iPhone's growing power as a marketing tool, the App Store alone accounted for 22% of post-click actions in September, a 6% gain over the prior month. "This is a true indictor of brands promoting their products and services via iPhone applications and including them as part of their overall marketing buy," stated Millennial's monthly ad metrics report http://www.millennialmedia.com/research/.

Buying a subscription made up 31% of post-click actions, followed by submitting a form (26%) and watching a video (25%). Among other findings, the study found that average monthly page views dropped slightly to 109 from 111, but mobile Web session time increased from four minutes, 59 seconds to 4:78.

The use of rich media increased 1% to 18%, and more than half (54%) of campaigns used frequency capping. The average number of ad requests per page was 1.6.

Among targeting methods, run-of-network was the most popular during the third quarter, increasing share 12% month-over-month and accounting for 28% of mobile campaigns. "With an overall focus in volume-driven campaign goals, advertisers were interested in reaching a large audience," according to Millennial.

The top advertising categories again included entertainment (movies, music and games), portals and directories, dating, consumer packaged goods and retail and restaurants.