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In the game of chess, there is a saying: "the threat is greater than its execution." As applied to the threat being used to justify eliminating Habeas Corpus (terrorism) is greater than its execution (actually blowing up things). The response (elimination of our civil liberties in response to security concerns) is a result that could not have have been achieved without the threat.
But we should be reminded of a saying attributed to Benjamin Franklin: "Those who would give up Essential Liberty to purchase a little Temporary Safety deserve neither Liberty nor Safety."
For more on the basics of Habeas Corpus see this entry at Answers.com (particularly the entry from the Legal Encyclopedia).