While the Apple App Store has grown to contain over 50,000 apps in less than a year, the most popular apps are generating the majority of usage by consumers. AdMob has released its Mobile Metrics Report for May (pdf), which examines the distribution of consumer usage of iPhone applications.

Highlights from the May 2009 AdMob Mobile Metrics Report:

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

- 14 percent of applications had between 10,000 – 100,000 active users, representing 322 applications.

- 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 (OS) 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.

Let’s take a look at some graphical info:

"As expected the top several percentage of apps are the big winners, with hundreds of thousands of users in a given month," says AdMob on the company’s blog. "But there are still a significant percentage of apps with a strong base of users outside the blockbusters.  As more and more iPhones and iPod touches are sold worldwide, usage of the medium and long tail of apps should increase.  In fact it is some of these niche apps that appeal to a limited set of users that makes the iPhone such a personal device."

The App Store must be seeing quite a bit of trafffic currently as the new iPhone 3G S was recently released (as well as the OS 3.0 update). What are your favorite iPhone apps? Tell us which ones you use the most.