I can't believe that you have been here at FR so long, and have Dr. Keyes on your homepage here, and have yet to figure out that the most unique thing about American government is that because we recognized that unalienable rights exist, we place explicit limitations upon government. You are advocating that the ends justifies the means. You are playing into the hands of fearmongers who are using this time of trouble to RUN to implement all kinds of things that 3 weeks ago could NEVER have been implemented. What evidence do you even have that such a system would work at stopping terrorism? NONE. And it can't be done quickly either. Or noninvasively, because I guarantee you that if I were a terrorist, I would be sure to sign up as many fake names as I could right away while the system was still soft; and then, with a "safety card" everyone will trust me and I can get away with anything! (Next, since you have nothing to hide of course, you will want implanted IDs to make it harder for a simple individual to use more than one ID).
If you permit this lapse into fascism, it will never go away and will be more and more and more abused. Where is your courage?