The Apple iPhone overtook the Motorola RAZR to become the number-one selling handset purchased by adults in the U.S., according to a new report by market research firm The NDP Group. The RAZR had lead NDP's rankings for the previous 12 quarters.

“The displacement of the RAZR by the iPhone 3G represents a watershed shift in handset design from fashion to fashionable functionality,” said Ross Rubin, director of industry analysis for NPD. “Four of the five best-selling handsets in the third quarter were optimized for messaging and other advanced Internet features.”

The RIM Blackberry Curve, LG Rumor and LG enV2 rounded out the top five.

With voice no longer providing the level of income carriers had become accustomed to over the years, operators have increasingly turned to data services, such as messaging and video, to raise average revenue per user (ARPU). It is well known that smartphones earn carriers greater ARPU than voice-centric phones.

The growing popularity of smartphones like the iPhone and BlackBerry show that a growing number of consumers are starting to want, if not demand, their new mobiles support the data-related services the operators are purveying. For instance, NDP reports mobile phones with QWERTY keyboard experienced the greatest year-over-year rise in sales—up to 36 percent of consumers were motivated to buy a phone because of this feature. That's up from a mere 11 percent of consumers during the third quarter of 2007.

Not all consumers are sold on data services, however.

“A growing data divide continues in cellular handsets,” Rubin added. “Those who see the value in wireless Internet access are justifying the investment, whereas voice-centric users have little incentive to upgrade, which is obviously detrimental to operators who seek to sell data plans and media access services to their subscribers.”

The more folks carriers can get to move into the former category the better off their bottom line. Especially in today’s poor economic climate, where the demand for cell phones declined by 15 percent to 32 million units from the same period a year ago.

Last spring, before the release of the iPhone 3g even, M:Metrics reported that iPhoners access the Web through the device's easy-to-use Safari application far more than users of other smartphones do through their browsers.

So while 58 percent of smartphone users connected to the Internet for news and information, a far larger percentage, 85 percent, of iPhone users did the same.. Only 13 percent of standard cell phone users accessed the Web from their mobile handsets, according to the report.

It wasn't just the superiority of Safari that made the iPhone such a much-used conduit to the Web. The mini applications known as Widgets that Apple bundles with the iPhone and AT&T's unlimited plan for data access were important too.

No doubt the launch of the iPhone 3G, with much faster data access, and the iPhone 2.0 software update, with support for third-party applications, and the roll out of the iTunes App Store's have served to make the iPhone platform more Web friendly.