• by Mark Walsh  @markfwal, June 13, 2012

Mobile marketers are increasingly targeting ads by audience rather than content, leveraging consumers’ “real world actions” to send them ads relevant to time and place, according to mobile ad network Millennial Media.

The ability to use location and other data to serve people ads based on where they are and what they doing in the physical world has long been the promise of mobile advertising. Marcus Startzel, Millennnial Media general manager, North America, emphasized the growing shift to audience buying from contextual advertising in mobile during a presentation Tuesday at the Mobile Marketing Association conference in New York.

As one example, he cited the ability to target a car ad to a mobile user after that person left an auto dealer’s lot. “Observed real-world behavior. If you’re on a car lot, you’re probably going to buy a car,” he noted. By contrast, it’s harder to tell if someone defined as an auto intender -- browsing auto-related sites a few times in the last month -- is truly in the market for a car.

Instead of serving the right ad in the right place at the right time, Startzel talked about finding “the right customer in the right place at the right time.”

Mobile ad exchanges like Nexage have the same goal of using location as the key attribute to audience targeting in mobile. However, whether people want to be tracked through their mobile devices -- even anonymously --  to receive more relevant ads, is still playing out.

Among other top trends in the first quarter, Millennial Media pointed to increased ad spending from the year-earlier period and developers bolstering ad buys to promote their apps. The company did npt provide any actual dollar figures in connection with those findings.

When it came to ad categories, sports was the fastest-growing vertical in terms of spending -- up 287% from a year ago -- followed by news, travel, CPG and health. Each saw triple-digit growth. But those gaudy increases were likely a result of starting from a small base. Despite its growth, for instance, sports still failed to crack the top 10 ad categories on the Millennial network, which includes telecom, finance, travel, retail and restaurants and entertainment.

Android remained the dominant mobile platform in the first quarter, accounting for 49% of impressions on the network, compared to a third from iOS, and 14% from BlackBerry devices. Smartphones generated nearly three-quarters (73%) of impressions, followed by connected devices (20%) and feature phones (7%).

Separate data from mobile marketing firm Velti on Tuesday showed a reverse pattern, with iOS representing the bulk (59%) of impressions compared to 41% for Android for the three months ending in May. Helping iOS to widen its lead from 55% in April was the overshadowed iPod Touch, which drove 14.9% of impressions -- more than the iPad and all Android devices.

The Velti report also pointed out the new iPad, released in March, is growing more slowly than its predecessor as an ad vehicle. The iPad 2 at the same point in its life cycle accounted for 21% of impressions, while the new iPad has 13.4%.

Among carriers, AT&T led the way with 53% of smartphone and tablet impressions, with Sprint and Verizon tied in the No. 2 spot with 23% each. T-Mobile had just 1%.

Apart from advertising, Velti said average transaction volume on its ZayPay platform increased 9% in the last three months to $3.22. That’s not quite a threat to Amazon yet. The most common purchases were for virtual currency, donations, software downloads and physical goods.

The Velti findings are based on data from its Mobclix Exchange, serving ads across more than 33,500 apps.