In response to a freedom of information request, the department of Homeland Security posted its Analyst’s Desktop Binder (a manual for the agency’s security analysts) containing this hotlist. The keywords cover domestic security, HAZMAT and nuclear, health concern, infrastructure security and other threats.
I remember back when I was a student and first heard about ECHELON and Carnivore I started adding such random words (a small dictionary subset I thought might be interesting to the Feds) in my signature, via a script. The way to fight against government idiocy and privacy intrusions is to show them how dumb and ineffective they are and the best way is to add such words randomly and automatically in your emails in a different color (or with the same color as the background so that your intended recipient is not confused) if not in the body, at least in the sig. Once they see their program being spammed by someone who is not a terrorist they might add you to a whitelist. If enough people do it, they might discontinue it altogether. (OTOH, with unlimited resources, there is little pressure to discontinue non-performing money-sinks.)
Furthermore, I know terrorists are incredibly stupid, so much so that even the brainless grunts working in government security can claim they are “intelligent” in comparison, but wouldn’t they be using encryption by now (PKI/ GPG)?!