much as I hate to agree with the man...
Thomas C. Greene makes a point that had been bouncing around in my head. Which is that, well, since so much secrecy surrounds the source of a lot of the information that the Bush Administration lean on for their terror alerts, should they not also conceal the targets, heck, even the fact that they have the knowledge, the better to pounce on Al Q when the attempts go ahead?

no subject
And, as far as I can tell, all elevations in alert levels serve to do is increase the number of random, circumstantial and otherwise unwarranted busts of US residents, few of which appear to be relevant to whatever information was key to the alert.