Britney and Rihanna hit the stage at the 2011 Billboard Music Awards for a sexy performance of "S&M." But one thing you might have missed,  was a quick smooch between the two pop stars at the end of the duet. The kiss didn't linger like Spears' infamous kiss with Madonna at the 2003 MTV Video Music Awards, but ABC didn't take any chances and quickly cut away to a shot of the audience. We have the photo though!