The terrorist watch list has been beset with problems ever since it came into existence. Ted Kennedy showed up on the No Fly List, a cousin to the terrorist watch list, back in 2004. 8 year-olds can't get themselves off it. Clearly, the smaller and more focused a watch list, the better for national security as well as civil liberties.

So of course, in reaction to the failure to track Umar Farouk Abdulmutallab last year, the federal government has gone in the opposite direction. Instead of double-checking the watch list and making sure resources were focused on legitimate threats, they made it comically easy to get placed on the watch list.

The failure to put Umar Farouk Abdulmutallab on the watch list last year renewed concerns that the government's system to screen out potential terrorists was flawed. Even though Abdulmutallab's father had told U.S. officials of his son's radicalization in Yemen, government rules dictated that a single-source tip was insufficient to include a person's name on the watch list.

Since then, senior counterterrorism officials say they have altered their criteria so that a single-source tip, as long as it is deemed credible, can lead to a name being placed on the watch list.

Keep in mind that current watch lists already boast over a million names, with 440,000 on the terrorist watch list alone. Keep in mind that most of these names are outdated or just plain wrong, according to a report from the Justice Department's Inspector General from last year. Keep in mind that, once you get on a list, it's virtually impossible to get off. The last possible response to any of these facts is to make the watch lists even bigger, relying on even less evidence, making them that much less easy to manage.

Law enforcement can absolutely benefit from a good watch list, and arrests thwarting attacks can and do result. And elsewhere in the piece, government officials maintain they have corrected errors and thinned down the problems with the lists. But there's a balance here. A single-source tip, "deemed credible," (whatever that means) seems like a thin reed for placement on a list of this kind.