"Do most people have something to hide that is so shameful, so damning?"
Have you ever complained to a friend or family member about your boss? Then the answer is yes.
Have you ever said something really embarrassingly politically incorrect? Then the answer is yes.
Have you ever possessed an illegal drug, including alcohol while underage? Then the answer is yes.
Surely that power comes not from the honesty of the words in the diary, but from the fear that those words become widely known. Do most people have something to hide that is so shameful, so damning? In many cases is secrecy a luxury we might quickly be happy not to have? Is this current need for privacy because society is less accepting of us as people? Perhaps our obsession with privacy is the problem, not the solution.