It's here!!!  The collaboration of the year has just impacted Earth.  The world has finally come to an end - maybe we should all dance "till the world ends."  Late yesterday Rihanna took to Twitter teasing her fans that she had a remix of her scorching hot single coming up soon with a guest feature on it.  Little did anyone know that it would be the legendary Miss Britney Spears.  Earlier this morning Rihanna premiered the song, and what a jam it is.  Like I've said before, 'S&M' is probably my favorite Rihanna song ever, and it comes as no surprise that Britney's favorite song at the moment is the same.  Britney's a sex symbol already, so she was already perfectly suited to the song.  While her vocals are not as strong or as powerful as Rihanna's are on the song, Britney brings her signature breathy lyrics and moans and groans to the song.  I love it so much, and I am really hoping they film a video for it or at least perform together. They're definitely giving GaGa and Beyonce a run for their money.