It was recently changed to make sure you have a balanced number of games as both colors. There was an overwhelming number of game seeking people to play with black pieces as opposed to white, so we no longer have the option. I think it's for the best personally. I know I always choose to play as white, so this'll balance me out more :P
How do I setup to start with white pieces? When I first started playing live I always hadwhite pieces. Suddenly, I only have black to start. Why?