• by Mark Walsh  @markfwal, July 16, 2009

When it comes to mobile ad spending, the entertainment sector led the way in the second quarter followed by telecommunications, Web portals, dating, and retail. That's according to the latest metrics report from mobile ad network Millennial Media, which says it reaches nearly three quarters of U.S. mobile Internet users, or 44 million people.

Within entertainment, movie studios accounted for nearly two-thirds of spending, followed by games (16%), TV (9%), other (7%) and music (4%). The big summer movie season clearly helped drive the studios' mobile advertising, with Millennial handling 17 campaigns for new movie releases such as "Star Trek" and "Transformers: Revenge of the Fallen" during the quarter.

Over the last year, the company says entertainment advertising has increasingly shifted from placements for endemic products like ringtones to more campaigns for more traditional media like movies and TV shows. The company didn't provide actual ad spending figures or share of spending by industry sector.

Millennial also said brands continue to invest in their permanent mobile presence, with traffic driven to their mobile sites from ads increasing more than 10% in June. In terms of campaign features, nearly half (48%) used frequency capping, 97% used image ads (versus text ads) and 17% of advertisers employed rich media in ads.

The average user session time in the second quarter jumped from the prior quarter from 4 minutes, 28 seconds to 5:38. That increase suggests people may be spending more time on mobile devices because they're on vacation or out of school and on the go.

As far as devices, Millennial's network saw a 68% increase in impressions from the iPhone and iPod touch. The increases stems partly from Millennial adding new publishers with iPhone-tailored mobile sites as well as the release of the iPhone 3G S in June.

That surge helped the iPhone regain the top spot among devices in share of impressions overall, at 8.6%, after yielding the no. 1 slot last month to the Samsung Instinct. Among manufacturers, however, Samsung held the top spot with 22.5% of impressions compared to Apple's 16%.