True; but you sleep well because you know that only your neighbors are likely to see that your new Ferrari is parked in your driveway. If, however, that is announced to the entire planet, including thousands of car thiefs in your area, I'm sure you'd be not sleeping at all.
Or, I could realized that as my ferrari is being displayed in public view, and is likely to be seen by someone who wishes to steal it, regardless of whether or not an old image on the internet may or may not contain it.
While your example of a conversation may not be black and white, this is. As you say, you can have a private conversation in public. You cannot, however, have a private display in public. If it's out there, it's out there.
Understanding is always the understanding of a smaller problem in relation to a bigger problem. -- P.D. Ouspensky