In the old country, there was a story ( which since I heard variants of ) my parents told me trying to explain why it is not a good idea to share details of your life with strangers, which goes something like this.

Secret police was trying to recruit a dissident to be their informer, but he was resisting. They tried to bribe him. They tried to cajole him. They tried to threaten him. He did not break.

One day a senior agent went by to introduce himself. When the dissident started to protest, the senior agent waved him away. 'We already know everything there is to know about you. We even know you drink tea and not coffee.' The treats, speeches and monetary gain had no hold on the dissident, but when he learned someone close to him betrayed him, he internally gave up.

The moral of the story is and always has been the same. Information is valuable. You may not think it is, but someone does. Do you think that someone has your best interest at heart?

I don't disagree with your anecdote in general. But it is somewhat interesting that, in the modern world, the implicit threat of an authority figure knowing this bit of trivia about you wouldn't be all that threatening. To the person in the story, it implies someone fairly close to him is giving information. To us it would be like "did get that bit of information from my Google searches, Facebook likes, or did you go through the effort of asking my bank where I shop?"

This is the part that interests me the most. In a way, its a thousand times worse now. In a practical sense, if the story was told today the story would suggest that any agent would get this information just by asking ISP, banks and maybe Amazon for your history with them. We don't just know that you drink tea. We can predict your daughter is pregnant and know wife is cheating on you. Full blown surveillance requires little to no effort. The amount of mind games you can play with that treasure trove is why you hear concerns IC about people 'going dark'.

I suppose to me how the information is obtained is secondary. The fact that it is obtained at all is an issue. We are only recently becoming better at analytics and seeing patterns that would be considered a little creepy only few decades ago. It is normalized now.

To your point that in the story, the trivia is truly irrelevant. By itself it means nothing. State knows I drink tea. Big whoop. Tons of people these days voluntarily show off eating pastas of all kinds. It is just serves as a way overwhelm the target with a feeling of helplessness ("They know everything"), abandonment("Someone close gave them information"),hopelessness("What is the point?").

So the trivia is not threatening by itself. It is the implication that the agent knows you very well indeed and that knowledge includes trivia.

Now imagine a person visiting you with a short listing of your detailed interests, search history, suspected health issues and inferred psychological profile.

It is a lot less subtle, but it conveys same message ( I know you better than your family, doctor, bookie.. ).

Sorry for the long response, but I just wanted to make sure it is clear that trivia is just a small part of it. As Dennis Reynolds would have said: It is the implication.

This is a fantastic comment. And it perfectly answers why the idea of "having nothing to hide" is so dangerous. Everyone will one day have something worth hiding, and probably not something illegal at all.

This really can't be overstated. Propaganda was highly effective even as words on pieces of paper distributed once a week or infrequent AM radio broadcasts.

I believe the old idea that would hold even more so now is that the only defense against propaganda is essentially to be illiterate. It is really hard to propagandize a person who can't read. The more informed a person believes themselves to be about the world from text, the more propagandized they are. I believe that is from Edward Bernays.

Illiterate people can listen to radio (or now, videos) just fine, though. Text isn't special, the content is.

Illiterate people can also be lured into crowds marching with photos of their leaders, de facto becoming themselves part of the propaganda.