Although I jest in my post, I have been closely following the info. on recent "Near Earth Objects" on the NASA site. One that is coming near soon is "Ikotawa #25143", scheduled to be near Earth next week around June 24th. Another is "Toutauis" (sp?), scheduled to be close in September.
I can't even wrap my mind around the scope of such an events; and the effects afterwards.
Then read Lucifer's Hammer by Niven and Pournelle.
This is something we need to be serious about. Planning and hardware must be in place when (not if) the event occurs. You can't throw something together at the last minute and expect it to save our butts.