Friday's spectacular meteor explosion in Chelyabinsk, Russia has left as many as a thousand people injured after a powerful shockwave blew out windows and set off car alarms. It may be the most destructive meteor in over a century, but the Russian people might to fortunate to be only replacing windows. The large explosion occurred several kilometers above the surface, giving the shockwave a chance to dissipate some before reaching the ground.
Early estimates have placed the size of the blast at about ten kilotons of TNT (Update: It could be more like 300 kilotons). Such an explosion would be similar in size to those from the nuclear weapons used at the end of WWII. Both kinds generated a powerful blast wave, but the weapons were detonated only a few hundred meters from the surface. That's about ten times closer than today's event. Of course, a meteor also doesn't release harmful radiation.
An event of this size isn't actually all that uncommon. A rock this size is expected to hit the Earth every few years, so why don't we see such dramatic videos every time? The answer lies in where these objects hit. Two-thirds of the Earth is covered by water, and much of the land is sparsely populated or uninhabited. For example, the last event of this size occurred over a remote part of Sudan, away from the cameras of bystanders. The largest event in modern history occurred in 1908, again in Russia. In that case, an explosion hundreds of times more powerful occurred and destroyed 2000 square kilometers of forest. Such a blast is similar to modern nuclear weapons. No one was hurt, but hundreds of thousands of trees were destroyed.
If you happen to find a piece of the meteor, pick it up! Even a tiny flake can be worth hundreds of dollars and meteorites are sought by both collectors and scientists. There is sure to be some pieces to find after this one.