Are there 400,000 terrorists plotting the destruction of America?

Call me skeptical, but the Washington Post reports that’s how many people are on the FBI’s terrorist watch list.

During a 12-month period ended in March this year, for example, the U.S. intelligence community suggested on a daily basis that 1,600 people qualified for the list because they presented a “reasonable suspicion,” according to data provided to the Senate Judiciary Committee by the FBI in September and made public last week.

The ever-churning list is said to contain more than 400,000 unique names and over 1 million entries. The committee was told that over that same period, officials asked each day that 600 names be removed and 4,800 records be modified. Fewer than 5 percent of the people on the list are U.S. citizens or legal permanent residents. Nine percent of those on the terrorism list, the FBI said, are also on the government’s “no fly” list.

One wants the government to be vigilant about protecting the country from terrorists, of course, but there’s a danger opposite to that of not investigating enough people and that’s investigating too many people. Leave aside, for the moment, the dangers to civil liberties; I’m willing to be a substantial portion — maybe even most — of the names on that list have nothing at all to do with terrorism. But they’re still consuming some of the FBI’s investigative resources. And time spent investigating the innocents might well cause the FBI to overlook the next Mohammed Atta.

In any case, it’s possible that the FBI will do everything as well as can be done — and that a terrorist will still slip through anyway. But the job might be easier if investigators weren’t flooded with so many (probably) false ledes.