If your friend or partner left his or her email open, would you look? How about a journal? Have you ever peeked at something private?
We haven't gone to great lengths to hide our email displays. I've seen a few of my friends' email (usually in the context of "hey, come look at this!") and I'm sure someone has peeked at mine too. It's not really that interesting. As for journal, well, it's all out here anyway.