@taboo:
when you stop living, you will DIE
Haha, nice try, but that's wrong! People die when they are killed! 
@Greg:
I believe there's a few asteroids on near miss/possible impact courses with us. And although it makes a great headline (or shitty popcorn summer flick or two) there are actually methods already in place and being researched regarding asteroid defense by creating a field around it to redirect it. I shit you not. I made a post about it a few months ago in the Random News thread.
$12,000 and two year's worth my life have taught me that such isn't a likely scenario. You've got the religious fanatics (Rapturists) on one side of the political equation who would love for a natural disaster to happen since it's effectively a jump-start to the apocalypse, and something like that would require joint effort by multiple countries and the countries capable of doing it don't like each other.
Best course of action is to use nuclear weapons to divert the asteroid, but people will be afraid of nuke launching and there's no guarantee that won't just break the asteroid up into smaller pieces that can hit multiple areas of the globe.
Which could cause tsunamis or earthquakes as predicted in myth. Personally, I'd like to see the HAB theory come into effect, making Africa the haven of the world, or alternatively global warming could drown the US, freeze Europe and thaw Siberia.
Either way, the Russians or Africans win. In the case of the asteroid, it's the penguins (I'm looking at you, ocean!). 