A few years ago, a friend and I were talking about using the redundant bits in web images to store text messages. You could drop the image into binary/hex editor and see the message or something like that. We discussed it as a means to increase the accessibility of web images. Screen readers could see descriptive information inside images so treated. Anyway, considering recent events, some folks seriously considered this as a means for bad guys to communicate with each other. Their search for such hidden messages has so far turned up empty.
Speaking of security and the erosion of privacy and personal freedom through technological advance, Dr. Steve Mann, has been observing the observers for some time now. Basically he is a gargoyle. He wears a uniform filled with computer, telecommunications and recording gear and walks around recording, receiving and transmitting stuff. He finds it telling that the people who most object to be being observed in this manner are the ones who observe and record everyone else for security purposes, that is police, government offices, casinos, retail stores and so on.