If they lean over my shoulder and read my screen intentionally, they've taken a specific action to do so and I'm comfortable defending myself on the basis that in that case I had an expectation of privacy, and if they were offended by what they read while they were violating it that was their problem.
As public figures (celebrities, politicians) have found out, once the information is out there, how it was obtained seems to be unimportant except in court. It won't really matter what your expectations were when it goes public.
I do find this tragic but the way it is these days.
