Rockstar B crowd surfs during Halo Performance

I would have thought that Beyonce would have been the LAST person to actually crowd surf during a performance! She usually has like friggin a billion security guards around her. Maybe she was feeling a little more free that night. I wonder why she chose to do it during "Halo" though. I don't see it as a song you would throw yourself into the crowd for while you're performing. What do you think?