There are different science fiction books that talk about high tech 'dust' or other micromachines that otherwise exist almost everywhere in the world monitoring everything. While the exact imagined implementations may not work, I can't help but believe that micro technology could spell the end of most privacy. Humans simply exist on the wrong scale. Our voice, our actions all leave a large amount of entropy in the world to be picked up and monitored by things far smaller than we are and fed into larger networks.