Google's Android operating system continued to chomp at Research In Motion's BlackBerry U.S. smartphone market share stake, racking up 28.7 percent market share, according to comSore.
The market researcher said RIM closed December 2010 with 31.6 percent share, down 33.5 percent from November and 35.8 percent through October. The trend should be alarming to RIM, whose BlackBerry OS has lost two percentage points to Android for each of the last few months.
Microsoft Windows Mobile fell to 8.4 percent from 9 percent through November, as the company seeks to position Windows Phone 7 as a viable alternative to Android, iOS and BlackBerry devices.
The big story continues to be Android. The OS gained nearly 3 percentage points from the November count of 26 percent, when it first passed Apple iOS at 25 percent.
Going back to the summer, Android has grabbed 7.3 percentage points since September, suggesting the platform enjoyed holiday season sales from devices such as Samsung's Galaxy S line and Motorola Droid devices.
The momentum should continue this year, with the Motorola Atrix 4G from AT&T, the Motorola Droid Bionic from Verizon, the Samsung Galaxy S 4G from T-Mobile and the Kyocera Echo coming from Sprint.
ComScore's U.S. smartphone numbers arrived more than a week after mobile researcher Canalys said more than 33.3 million of the 101.2 million smartphones shipped worldwide in the fourth quarter 2010 were based on Android.
So, what of Apple iOS, the platform comScore claimed Android dethroned in the U.S. last month? ComScore showed that iOS remained at 25 percent through December. Apple's statistical stagnation is interesting considering the company shipped 16.2 million iPhones for 2010.
Analysts expect Apple to ship anywhere from 10 million to 20 million iPhones on Verizon, providing a stiff challenge to Android's rise.
Overall, 63.2 million U.S. consumers owned smartphones during the three months ending in December 2010, up from 61.5 million people through November and up 60 percent from a year ago.