Hey folks; aren't we getting just a little paranoid here?..............if the technology is in place I have three simple questions for you:
You have a point there nihil. Where was all of theses systems when we needed them he most.
But one thing that we have to remember is that , just because these systems are extremely modern and sufisticated they are still computers. Computers are programed to do what the programmer programs it to do. With this said there is a way to bypass this system with encrytion as the_JinX previously mentioned.

Most "smart" terrorists will use codewords so they will never be found using a word filter
So hopefully that will answer your questions.
Cheers BLUEWOLF !!