Only well-meaning twits unfamiliar with the algorithmic technology think you can use keyword spam to mess with the email spying system. It is a far more sophisticated mathematical technology and would require a very sophisticated attack designed by very knowledgeable mathematicians to spam. I've seen no one suggest an Echelon spamming technique yet that would defeat even a primitive implementation of the theory, and this is an area of mathematical theory I am very familiar with.
Fortunately, the terrorists are generally as ignorant as the internet using public in this regard. There is not that many countries that produce large quantities of decent mathematicians, never mind terrorist producing countries. Welcome to the future battlefield...