Apple's iOS leapfrogs BlackBerry in U.S. smartphone market share

Apple's (NASDAQ:AAPL) iOS is now the second largest U.S. smartphone operating system according to digital research firm comScore. As of April 2011, iOS accounts for 26.0 percent of all U.S. smartphones, behind Google's (NASDAQ:GOOG) Android at 36.4 percent. That relegates Research In Motion's (NASDAQ:RIMM) BlackBerry platform to third at 25.7 percent, down 4.7 percent from January 2011. Microsoft's (NASDAQ:MSFT) Windows Phone platform trails a distant fourth at 6.7 percent. Release