The fact that iPhone users are increasingly downloading applications from the Apple App Store presents a great opportunity for marketers that want to reach consumers on a personal level.

AdMob, a mobile advertising platform, examined the distribution of consumer usage of iPhone applications in its May 2009 Mobile Metrics Report. With more than 50,000 applications in the Apple App Store, usage is increasing dramatically.

"Usage of applications on the iPhone continues to grow, which in turn grows the opportunity and ability for marketers to connect with consumers through powerful and reach ad units," said Nicole Leverich, director of corporate communications for AdMob, San Mateo, CA.

"We were excited to see that the size of some of the top iPhone applications rivals that of the top mobile Web sites," she said. "Some of the biggest applications in AdMob's network were accessed by more than 1 million users in May."

AdMob found that 5 percent of applications had more than 100,000 active users in May 2009, representing 116 applications in AdMob's iPhone network.

Additionally, 14 percent of applications had between 10,000 to 100,000 active users, representing 322 applications.

More than half (54 percent) of applications had less than 1,000 active users, representing 1,244 applications.

The average iPhone user in AdMob's network accessed four applications in May.

Five days after its launch, the iPhone 3.0 operating system represented 44 percent of iPhone ad requests.

In contrast, only 1 percent of iPod touch requests came from devices running the iPhone 3.0 OS.

AdMob reached 15.1 million unique users on iPhone and iPod touch devices on 2,309 applications in its network in May, the majority of which were free to download.

"AdMob's May 2009 Metrics Report found that, as is true with many other forms of media, the most popular applications generated the majority of usage by consumers," Ms. Leverich said. "Few applications may reach this blockbuster of success, but there is also significant percentage of popular applications have built a strong base of tens of thousands of users.

"The long tail of applications that make up the majority of the App Store generated a minority of the total usage," she said.