According to new data released by comScore, the iPhone accounts for more than a quarter of U.S. smartphone market. As of December 2009, BlackBerry maker Research In Motion led U.S. smartphone platforms, with a 41.6% share—down from 42.6% in September 2009—while Apple ranked second with 25.3% of the market, up 1.2% percent from September. Microsoft came in third, with 18% of the market, down 1% from September, followed by Palm, which accounted…