Apple iPhone users in the United States are more likely to surf the Web than Android, BlackBerry, or Windows Mobile users, according to data released by AdMob.

The mobile advertising company compared data from more than 6,000 publishers and found that the iPhone accounts for about 50% of mobile Web traffic in the U.S. market and 33% of worldwide traffic. Apple's smartphone is widely considered to have one of the top mobile browsers. While the data is not definitive because it only measures AdMob's network, it's an indicator of mobile Web usage patterns.

Google's Android operating system also had a relatively strong showing, as it has captured 5% of the market. This is a decent showing considering there's only one Android device, the T-Mobile G1, and it was released about five months ago. The Linux-based mobile OS was built with Internet connectivity in mind, and it has deep integration with the search company's Web services.

Research In Motion's BlackBerry platform placed second for mobile traffic, with 21% of the U.S. market. While the BlackBerry Curve is a common handset for browsing the Web, RIM lost 11% market share since AdMob's August report.

Microsoft's Windows Mobile placed third with 13% of traffic, and Palm held on to 7% thanks to the success of the Centro. Globally, Symbian had been the leading OS for mobile Web usage, but it's quickly ceding ground to the iPhone. In the August report, Symbian had 64% of the market; it has fallen to 43%.

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