This region of Russia is known for meteorite occurrences of different sizes.The best known is the Tungus meteorite when a huge region in Siberia was destroyed. This event, called the Tunguska mystery, has not been solved until today.
If you check out Chelyabinsk on Google Earth (image above) and see how many meteorite impact marks there actually are. The region has been a target for meteorite impacts for some time already. Maybe this latest occurence was just coming before the bigger one that will pass by the Earth in the coming days.