The circle of secrecy never grows smaller, except by death. The confidentially of private mail, or of diplomatic communiques is supposed to be absolute, but of course such things sometimes do get out. With the secrets that archaeology and DNA can reveal, things that have been secret for thousands of years can now be known.
So we don't ask for the miraculous when it comes to privacy, but we do have expectations and some things are better than others. Memories of personal conversations can be challenged, giving a final possible escape if we are exposed. We have regarded phone conversations as potentially private (depending on what our agreements are with the other party), because they are - usually - not recorded. The phone message has changed that, as it can be recorded, kept, and used against you. Our habits with the phone in our hand betrays us into relying on a privacy that no longer exists.
On the internet, things we thought were private tend to move in the direction of being exposed. Twitter and Quora were never intended to be private, but some of the photo-based messages were intended to vanish immediately after one use. Except some of them are still around. Emails get leaked, and group emails should be regarded as especially vulnerable, increasingly so as the number of recipients grows. Listserves might stay private, but some have been leaked.
Group chat functions on text are currently uncensored by outsiders and generally quite private. They are becoming the vehicle of controversial discussion, as a small group which has built up trust can say things they might not readily share in other venues. If the group chat grows too large its vulnerability to someone exposing all increases. But most stay quite small - a family, a fantasy football league, a dozen like-minded friends discussing politics or religion. The San Francisco recall election was reportedly strongly influenced by the network of overlapping group chats, not entirely invisible but difficult to spot in the wild. Those of you who want to increase local political influence might consider it as a way to go - for now, and with caution. Private and uncensored. I don't imagine they will directly influence national or world affairs that much, but in aggregate they likely have some efffect.