Based on data it collected in November 2010, Nielsen reports that Apple improved its position in the U.S. market from 27.9% the month prior up to 28.6%. Apple's competitors aren't far behind, however, and Apple may not remain at the top for long.

During the same period, Google's Android platform surged from 22.7% in October to 25.8% in November. Apple's lead over Android was cut from 5.2% to 2.8% -- before the holiday shopping season kicked into high gear. Android held only 15% of the U.S. smartphone market in June 2010.

Research In Motion's BlackBerry platform lost ground to Android and iOS, slipping from 27.4% in October to 26.1% in November. That's just a hair's breadth above Android's position. In June, RIM held onto 33.9% of the smartphone market in the U.S.

Perhaps the most notable metric is how quickly Android is being adopted. Of those who have purchased smartphones in the last six months, 40.8% bought Androids, 26.9% bought iPhones, and 19.2% bought BlackBerries.

Also notable? The iPhone is only available from one carrier in the U.S., while Android and BlackBerry devices are available from nearly all the carriers. For Apple's device to have any lead at all given its more limited distribution speaks to the platform's popularity.

That could all change if Apple and Verizon team up for a device that is compatible with Verizon's network. A Verizon iPhone would likely lead to a surge in adoptions for Apple -- at the expense of Android and BlackBerry devices on Verizon's network.

Will that be enough for Apple to maintain its lead over the long term? Probably not. The Consumer Electronics Show launches January 6, and manufacturers across the board are expected to debut new Android hardware.

Google's Android platform shows no sign of slowing with respect to its growth, and Apple and RIM need to act if they want to remain leaders.