Samsung should send Google (GOOG) a thank-you note for developing the Android operating system. The South Korean electronics giant has taken Google's free-to-use, open-source software and built a massive smartphone business around it. In the fourth quarter, Samsung accounted for 31.1% of smartphone sales worldwide, putting it in the lead, research firm Gartner reported Wednesday. It was followed by Apple (AAPL), which uses its proprietary iOS