A piece of the rock

Another asteroid story.  Apparently there is a project going on that intends to locate all space objects that could pose a danger to Earth.

So by 2008 science will know (allegedly) every piece of space rock that poses a threat to Earth.

I feel sooooo much safer now.

I have some questions though.  If they find an asteroid bearing down on us, we'll need 30 years to take the proper action.  How do they know that, dinosaur textbooks?  And it would possibly make things worse if we nuked one on its way?  How can turning a big freaking piece of rock into pieces of gravel make things worse?  What, like it's going to mistakenly unleash the three villians from "Superman 2" from their trapezoid prison?

I suppose I am obsessing about this a little.  You can spend your enitre life worrying about things that will never happen.  But I do have to admit that I can't quite understand why more people aren't nuts about this.