Android tips the 51% mark in US share, iPhone nips its heels with 31%

 Dec. 2011 vs March 2012. The March smartphone market share tally for the US is in from comScore, and it paints a familiar picture that's rosy for Apple, Google and Samsung, but not so flush-cheeked for everyone else. Android is still tops and jumped almost four points to 51 percent of new American buyers. Apple's still riding high after shipping 35.1 million iPhones, however, and moved up to