Please read Jack Balkin’s excellent post on the The Twin Dangers of the National Surveillance State:
The twin dangers of national security displacing the criminal justice system and the criminal justice becoming increasingly like the national security system are consequences of technological change. Although the National Surveillance State arises from the changing nature of war, changes in technology do not stop with the problem of war, as least as traditionally conceived. Rather, the very same changes in technology threaten to transform the ways that democratic governments interact with their citizenry. That is why the debate over the NSA program is so incredibly important. We need to have a national debate on how we will implement a system of information gathering and processing that is quickly becoming the norm and not the exception. If we do not have this debate, the system will be implemented so as to displace the civil liberties and rights of citizenship we hold dear.