Bruce Schneier, writing in the St. Paul Pioneer Press, is of the opinion that the NSA's collected databases of U.S. Phone calls (if it actually exists) is a worthless exchange of privacy for not a lot security.

Here's the gist of his argument:

Just in the United States, there are trillions of connections between people and events -- things that the data-mining system will have to "look at" -- and very few plots. This rarity makes even accurate identification systems useless.
Let's look at some numbers. We'll be optimistic -- we'll assume the system has a one in 100 false-positive rate (99 percent accurate), and a one in 1,000 false-negative rate (99.9 percent accurate). Assume 1 trillion possible indicators to sift through: that's about 10 events -- e-mails, phone calls, purchases, Web destinations, whatever -- per person in the United States per day. Also assume that 10 of them actually indicate terrorists plotting.

This unrealistically accurate system will generate 1 billion false alarms for every real terrorist plot it uncovers.

Every day, the police will have to investigate 27 million potential plots in order to find the one real terrorist plot per month.

Clearly ridiculous.

That's a compelling argument, but I'm not sure it is one I'm willing to buy into.

One thing Mr. Schneier assumes is that these databases are being analyzed in a vacuum, separate from the countless other forms of intelligence gathered by government agencies engaged in anti-terror operations. I just don't see how that can be true. This call data is just one source of data, and the idea that our intelligence officials are following up on hundreds of thousands of leads produced by this data mining without first filtering it through intelligence gathered from other sources is patently absurd.

I'm no expert on intelligence matters, but I just don't think that is how this data is being used. Instead, I think these databases are being used to produce "puzzle pieces" to help complete the picture provided by other intelligence.

Consider this example:

Say a cell phone found in during a raid on a terror house in Iraq has some U.S. phone numbers in the call history. Isn't it nice that our intelligence community has a database of phone calls to run these phone numbers through so that we can find out who these people were calling and who was calling them?

I think so.

(via Pajamas Media and The Volokh Conpiracy)