Reply #2: we do spend money (and we do have some control) [View All]

NASA has an observation program:
http://neo.jpl.nasa.gov/
Close Approaches:
http://neo.jpl.nasa.gov/ca/
Torrino impact scale:
http://impact.arc.nasa.gov/index.html

Taxes pay for that. Though it isn't nearly enough.

Essentialy we're in the early stages of developing the technology needed to give us warning early enough so that we could at least attempt to do something to reduce the damage. Current technology doesn't have sufficient accuracy.
What can be done, and whether or not something can be done at all depends on the size of the impactor, and the technology that we have at that time. The good part is that meteorites and comets are more rare the bigger they are, and the biggers ones are more easy to detect. The bad part it that for the time being we can't really do much about the big ones.
As it stands now we might get just a few days warning of an impact by a meteorite large enough to wipe out a city (a 'small' meteorite*), and it would probably not be accurate enough to even start evacuating any possible impact area. My guestimate is that if we'd make a serious effort and spend more then just a few dimes on it (relatively speaking), in about a decade we could increase the warning time to weeks if not months and make it accurate enough that it's worth while. Beyond that it may eventually be possible to divert the smaller impactors. Way beyond that would be evacuation of the planet in case of an encounter with a planet crusher. It is only likely such a thing will eventually happen, provided the human race survives that long.
I'd say that in the short term it would be worth while to worry

(* of course there are many meteorites and comets that are still smaller but even though those may kill a few people (far more unlikely then being struck by lightning), those aren't really a hazard.)