[JimSEA]

That wouldn't be nice or, presently, preventable. There is a lot of concern about that however. This is one thing NASA is actually doing.

[MtnClimber]

Yes, detect it in time and a small spacecraft collision would nudge it off collision course.

[HiTech RedNeck]

This is where the problem enters a religious dimension. What do we do if something could easily wipe us all out? Do we look afresh at where our bread is buttered? Or do we just run around with our hair on fire?