Specifically, 9.6% of mobile users were connecting to a social network as of October 2008, compared to 3.4% in September 2007. The rapid growth is due in part to the small base of people who are social networking on mobile.

By 2012, eMarketer projects that more than 800 million users worldwide will participate in social networks via their mobile device, up from 82 million in 2007.

While the total base of mobile social networking users will remain under 20% by 2012, eMarketer believes "that these users will have a disproportionate impact on marketing, media and mobile communications because creating and sharing digital content (user-generated and professional) forms much of the social networking experience."

Research released by Nielsen Mobile in September showed that 21% of U.S. mobile users recalled seeing an ad while accessing social networks and blogs. That compares to 57% who recalled seeing an ad while browsing the mobile Internet overall.

Mobile social networking is still more prevalent outside the U.S., according to eMarketer. It points to the growth of mobile-only social networks such as Germany's itsmy.com, which has 2.5 million registered users. Facebook in November said use of its mobile services had grown from 5 million to 15 million during 2008, but did not break out usage by country.

As of Monday, Facebook had the 12th-most-downloaded iPhone application in Apple's App Store.

Among other key findings from the Kelsey study, 15.6% of mobile users used their phones to search the Web for local products and services, compared to 9.8% a year ago. And 14.3% searched outside their local area, up from 6.4%.

When it comes to media consumption, 8.4% watched a music video or other type of Internet video on mobile devices--nearly double the 4.4% from 2007.

The research results were based on online surveys completed by 512 U.S. mobile subscribers ages 18 and over.

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