The world’s biggest musical acts took to the stage Sunday at a massive outdoor concert on the majestic steps of the "Lincoln Memorial": Bruce Springsteen, U2, Sheryl Crow, Steve Wonder, James Taylor, Shakira, Pete Seeger, Harbie Hancock, Mary J. Blige, Denzel Washington and Tom Hanks, and others. Still, the star who shone the brightest was the man who sang nary a note, Barack Obama, who enthralled a...