There's a great op-ed piece in Wednesday's Wall Street Journal by Pete Du Pont on anti-missile defense.

As to cost, Mr. (Joe) Biden estimates that an antimissile defense system would have a price tag "well over $100 billion." To put that in perspective, the Sept. 11 attacks cost the economy maybe twice that. Recently 54 senators voted in support of a farm subsidy bill that would have added $75 billion to existing farm subsidy programs. In any case, to paraphrase humorist P.J. O'Rourke, a missile defense is cheaper than filling the hole that used to be San Francisco.

If we can make an anti-missile defense that saves just one U.S. city from a foreign attack, then it's worth the money.