Taylor Swift doesn't mind sharing the spotlight - even at one of her own concerts.  She treated fans at her LA show to a special guest performance from teen heart throb Justin Bieber.  When the band launched into a cover of Bieber's hit 'Baby,' the crowd went wild.  Taylor later tweeted  'You think you've heard LOUD screaming in your life.. Then @justinbieber comes out and does a surprise song during your show. Woah. Unreal.'  Check out the video.

Taylor Swift & Justin Bieber