David Letterman revealed the cover of the 2011 Sports Illustrated swimsuit issue featuring Russian model Irina Shayk on Monday, surprising his audience and Shayk, too."Of course I didn’t know," said Shayk, who cried on camera after the revelation was made on "Late Show with David Letterman.""Alright, drop the deal," said Letterman, instructing the veil to fall from the New York City billboard portraying the magazine cover. (ETonline.com)