How do you send messages over the Internet when one of the most powerful spy agencies in the world is watching you? The answer is spam. After 9/11, the Taliban tried to hide messages from NSA surveillance by disguising them as spam emails, and it worked, at least for a little while.
By writing messages with spam-like subject lines, combatants were attempting to exploit surveillance filters so that instead of being combed, the messages would be sorted into the spam folder abyss.
Usually getting sent to the spam folder is a bad thing, but it's exactly what the terrorists wanted. One message that Taliban combatants sent had the headline "CONSOLIDATE YOUR DEBT." It looks like the same generic headline that could get an email sent to the spam folder in your Gmail account worked against the NSA's algorithms.