On Friday, socialite ex-con Paris Hilton sat down with David Letterman on "The Late Show." Paris wanted to promote her clothing line, her movie, and her perfume, but there was only one thing Letterman was interested in discussing: her life behind bars. As far as PR rehabilitations go, this was not at all like the smooth move that publicist Dan Klores pulled off when he set up Paris to go on "Saturday Night Live" to defuse the news of her sex tape.