[mastequilla]

But that doesn't mean we shouldn't try to stop them anyway.

True, but we shouldn't expect the system to be foolproof. Had we done some of the more extreme suggestions posed in this thread, such as ban all arabs/muslims from flying, it wouldn't have stopped Vincente Padilla, John Lindh, (or perhaps even Richard Reed) from carrying out an attack.

Remember that the 2nd most devastating terrorist attack in U.S. history was carried out by a yokel in Oklahoma.

[GBA]

A conspiracy of "yokels", with military training, and possible middle eastern connections. INHO, the OKC bombing isn't the best argument to use if you are suggesting that a single individual managed that attack.

Stopping every attack may or may not be possible, but it is a worthy and necessary goal.