New data on the top 10 mobile phones puts Apple on top due to the sheer number of iPhone owners. But both Research In Motion and LG actually control more market share because they sell multiple, popular models.

Nielsen's data on the top 10 phones in use in the U.S. from January through October shows Apple with 4 percent market share, RIM with 6.3 percent, and LG with 6.4 percent. But the trio lead a very fragmented market. In fact, the top 10 phones account for just over 20 percent of the total devices in use.

With an estimated 271 million U.S. mobile subscribers at the end of 2008, accounting for about 88 percent of the U.S. population, even 1 percent market share is significant.

RIM BlackBerry devices and LG handsets--voluminous in offering compared with the singular iPhone also have the benefit of longer time on the market and of promotion by the carriers that don't have the iPhone. LG is the No. 3 handset maker behind Nokia and Samsung. RIM and Apple have nowhere the number of models offered by the top three handset makers, yet they enjoy a stronger market share.

The Nielsen data shows both the opportunity and the challenge of creating the next big thing in mobile devices. Just a few years ago, Motorola's Razr was the belle of the ball, and RIM was firmly fixed as an enterprise device. However, the convergence of voice, e-mail, and browsing, as well as new 3G networks, brought the smartphone to the forefront and helped push both RIM and Apple to the top.

All hope is not lost for currently less popular handset makers, as the market can very quickly change dramatically.

Indeed, there is a big challenge under way from Android-based phones such as the Droid that could thrust laggards such as Motorola back into the spotlight, provided that Google doesn't stomp all over the developer community that has been building up around the new mobile operating system.

And mobile phones are not just for those on the run. Nielsen's Convergence Audit (PDF), an annual survey on voice, video, and data products, "shows a rise in households who have 'cut the cord' by trading their traditional landlines for wireless cellular services and an increase in mobile media device usage among a diverse set of households."

In the second quarter, the report said, 21 percent of households were using wireless cellular service only--compared with 18 percent a year earlier. "This increase comes from...households who have dropped their landlines as well as from young adults that started new households with just a wireless phone service," the report said.

Odds are that these percentages will continue to climb as young mobile users reach adulthood and as adults look to their mobile devices to do more than just make calls.