Abstract: The Giggle Factor (GF). Mention Planetary Defense and you'll soon understand. Even without invoking the sinister vision of alien beings arriving to enslave or destroy humanity, the eyebrows of serious and senior members of the national defense and scientific communities go askew when the subject is broached, whether at cocktail parties or congressional budget hearings. Even the most ardent supporters of defending the Earth from cataclysmic cometary or asteroidal impacts share occasional public or private chuckles with colleagues and skeptics behavior considered unthinkable when discussing means to avert or mitigate the catastrophic epidemics, wars of aggression and genocide, and terrestrial natural disasters that have peppered man's history on Earth. But the GF doesn't diminish the evidence that the threat exists; measurable and historic, but largely unpredictable. It does, however, continue to cloud a serious issue by generating a unique mosh pit of government branches and agencies, international groups, and private and public research organizations and corporations that would love credit for the resulting system (if it were ever successfully employed), gleefully accept a slice of the multi-billion dollar pie that would accompany a full-fledged planetary defense system, or justify continued funding and development of systems that could be tied to a planetary defense mission. Saddling each of these players, though, are the negative connotations of being involved in a publicly perceived high GF program that may never be used during a human lifetime, raises the suspicions of potential military adversaries, and may not work anyway.

Limitations:APPROVED FOR PUBLIC RELEASE
http://www.stormingmedia.us/59/5990/A599034.html

Yeah, a Planetary Defense Shield is like flood insurance in a desert. No offense to the President of the US who devised such a deal, but when you bring up ETs or little green aliens with blast rays . . . But, as far as the earth being hit by a gigantic planet- sized asteroid, well, it has happened before and recently we have filmed Jupiter being hit by 6 to 9 comets in a row. And we have one coming close by and for years, we'll have the reports of fragments of the tail of that comet on a collision course with earth! Should we hurry up now and build us some rockets to fire up there and blast 'em out of the sky? Maybe.