Via Kevin Drum, this Washington Post op-ed is the best explanation I've heard yet as to how a database of all domestic calls even *could* aid law enforcement through pattern analysis. But that's not saying much.
Let's take a hypothetical problem: An al-Qaeda operative decides to switch cellphones to prevent the National Security Agency from monitoring his calls. How does the NSA identify his new cellphone number? How does it winnow down a haystack with several hundred million pieces of straw so that it can find the deadly needle?But this still falls way short of passing the most basic test. If the NSA is monitoring a cell phone (thanks to a court order properly received) suspected of being used by a criminal and they suddenly realize it's no longer being used, then they can quickly get the proper subpoena required to look into the phone call patterns of the numbers the suspect has called in the past, and they can perform *exactly* the same analysis without ever having to have on file the calls I made or received this week. This is simply ridiculous. The idea that some super computer somewhere is going to gargle every phone call made in the US and then spit out the numbers of terrorists, in a way that it couldn't if it didn't have my records, just doesn't make any sense.
The problem may seem hopelessly complex, but if you use common sense, you can see how the NSA has tried to solve it. Suppose you lost your own cellphone and bought a new one, and people really needed to find out that new number. If they could search all calling records, they would soon find a number with the same pattern of traffic as your old one -- calls to your spouse, your kids, your office, your golf buddies. They wouldn't have to listen to the calls themselves to know it was your phone. Simple pattern analysis would be adequate -- so long as they had access to all the records.
And all of that disregards, as the piece (and Kevin Drum) points out, one other glaring issue with all this mass data mining. It's illegal.