Without getting bogged down in the details, it's obvious we're dealing with another case of where to draw the line between individual liberty and security.

Defending our privacy against all possible government threats will leave the same kind of gaping holes in our security that the first nineteen terrorists waltzed through. Had the information sluicegates between the FBI and the CIA been open, we might have nailed those guys. But defenders of liberty, for what seemed to be excellent reasons at the time, and may still be excellent reasons, declared that the functions of these two organizations must be kept separate. And so it went.

Clamping down totally on our citizens to the extent currently possible with computers and technology would certainly give us much greater protection against threats both foreign and domestic, but at the cost of scrapping a large part of what makes the United States the greatest protector of individual rights in the world. Privacy may not be protected under the Constitution, but I have a hard time believing that one could construct a Big Brother infrastructure and put it in the hands of the government, which (to put it mildly) tends towards collectivism, without other rights inevitably beginning to be infringed.

The real answer lies between these two extremes, and I'm afraid it's one no one will like, and would be political suicide for any politician proposing it:

To maintain as much physical security as possible, we may have to give up a few of our rights to absolute privacy. However, to maintain the individual freedoms that our nation supposedly treasures, we will have to exercise strong limits on our capacity to police our citizens. And the corollary to the latter is that we will have to accept losing a small chunk of our population to terrorism at intervals.

This position can be defended on the basis of hard logic, but I can't see defending it to an emotional populace.