Bruce Schneier makes the case:
We have no evidence that any of this surveillance makes us safer. NSA Director General Keith Alexander responded to these stories in June by claiming that he disrupted 54 terrorist plots. In October, he revised that number downward to 13, and then to "one or two." At this point, the only "plot" prevented was that of a San Diego man sending $8,500 to support a Somali militant group. We have been repeatedly told that these surveillance programs would have been able to stop 9/11, yet the NSA didn't detect the Boston bombings -- even though one of the two terrorists was on the watch list and the other had a sloppy social media trail. Bulk collection of data and metadata is an ineffective counterterrorism tool.
Not only is ubiquitous surveillance ineffective, it is extraordinarily costly. I don't mean just the budgets, which will continue to skyrocket. Or the diplomatic costs, as country after country learns of our surveillance programs against their citizens. I'm also talking about the cost to our society. It breaks so much of what our society has built. It breaks our political systems, as Congress is unable to provide any meaningful oversight and citizens are kept in the dark about what government does. It breaks our legal systems, as laws are ignored or reinterpreted, and people are unable to challenge government actions in court. It breaks our commercial systems, as US computer products and services are no longer trusted worldwide. It breaks our technical systems, as the very protocols of the Internet become untrusted. And it breaks our social systems; the loss of privacy, freedom, and liberty is much more damaging to our society than the occasional act of random violence.
It's all stuff he's said before, but it needs saying again.