Writing for The Motley Fool, Sam Mattera warns "Apple and Samsung Could Be Dethroned by Asus' Radical New Device" (tip o' the antlers to Paul Baptist)."Warns" is maybe the wrong word. This is more like some sort of interpretive dance that no one really understands.When it comes to the U.S. smartphone market, it's mostly a two-horse race. Cumulatively, Apple and Samsung sell two out of every three smartphones Apple, of course, sells more than 50 percent of the smartphones in the U.S., meaning that Samsung's share must be about 15 percent. So, one of those horses is Secretariat and the other one is Mr. Ed.But that could change next year, when Asus brings its PadFone to the Un