Comment Governance could be a problem... (Score 3, Insightful) 71
The technology sufficient to divert an asteroid, especially with limited warning(which precludes some of the subtler 'attach an ion drive or give it a slow shove with a laser' type schemes), is probably pretty punchy, possibly 'basically an ICBM but better at escaping earth's gravity well' punchy. It would be an unfortunate irony if, in the attempt to mitigate the city-destroying-asteroid threat, we ended up with some sort of proliferation problem or another round of delightful nuclear brinksmanship.
In an ideal world, you'd hope that people could put "Stopping asteroid apocalypse" in the category of 'things more important than your petty nation-states and dumb ethnic and religious squabbles'; but I wouldn't exactly be shocked if people largely can't and every stage of an anti-asteroid project ends up being a bunch of delicate diplomacy and jingoistic dickwaving between the assorted nuclear powers, along with a lot of hand-wringing about anti-satellite capabilities, and generally a gigantic mess.