The ever-vigilant satellites of the Nuclear Test Ban Treaty Organization watch the Earth, year after year, for evidence of nuclear shenanigans. Between 2000 and 2013, they found 26 nuclear explosions that didn't correspond with any known human activity—but seemed to correspond with meteor impacts. To put it another way, we get nuked about twice a year and most of the time we don't even know it.
The Chelyabinsk meteor, shown in the image above, was a clear exception. It collided with Earth's atmosphere at more than 40,000 miles per hour and exploded—because when you're going that fast, you don't run through the atmosphere, you run into it—18.4 miles above the surface of the Earth. The explosion damaged over 7,000 buildings and injured more than 1,500 people in the Urals region of western Russia. And since it was (as far as we know) the biggest thing to collide with Earth's atmosphere since the Tunguska event of 1908, it was freaking scary. YouTube users uploaded footage of the massive explosion, and its aftermath, here (I recommend turning the volume down, as the explosion is pretty loud):
Earth has a long and distinguished history of getting clobbered by asteroids and geologically erasing evidence that it ever happened, so it's not really a huge deal to the Earth itself. But given that Earth also has a history of experiencing mass extinctions subsequent to some of these asteroid impacts, our recent efforts to track asteroids (and maybe do something about them before they hit us) makes good practical sense.