Letterman Palin

FILE - In this Jan. 17, 2008 file photo, television talk show host David Letterman walks out of The Ed Sullivan Theater during a taping of "The Late Show with David Letterman", in New York. The late-night host, who ran afoul of the Palin family last year with a misfired joke, took it relatively easy on the young couple on Wednesday's July 14, 2010 "Late Show."(AP Photo/Evan Agostini, file)