This is an interesting nugget from a New York Post op-ed today:

In 2002, the feds (presumably the NSA) picked up random cellphone chatter using the words "Brooklyn Bridge" (which apparently didn't translate well into Arabic). They notified the New York Police Department, which flooded the bridge with cops. Then the feds overheard a phone call in which a man said things were "too hot" on the bridge to pull off an operation. Later, an interrogation of a terrorist allowed by the Patriot Act led cops to the doorstep of this would-be bridge bomber. (His plans would definitely have brought down the bridge, NYPD sources told me.)

Why didn't Bush get a warrant? On who? For what? The NSA wasn't looking for a man who might blow up the bridge. It had no idea what it was looking for. It just intercepted random phone calls from people in the United States to those outside — and so heard the allusions to the bridge that tipped them off.

In criminal investigations, one can target a suspect and get a warrant to investigate him. But this deductive approach is a limited instrument in fighting terror. An inductive approach, in which one gathers a mass of evidence and looks for patterns, is far more useful.

But, if the Democrats are to be heeded, it will no longer be possible.