In my opinion, there should be little reason to hide stuff from a partner, other than maybe embarrassing photos or hobbies where they feel like it's too early in the relationship to open up about yet. The issue is that giving an SO a password for emails, Facebook, and the like, enables them to view interactions between you and others prior to your relationship with them beginning, which may only serve to make an already insecure person feel needlessly even more insecure and defeat the supposed purpose of establishing more trust and eliminating insecurity. I don't have a passcode on my phone, but at the same time, I would feel uncomfortable if even my best friends looked through my personal conversation history in great detail, and I hate it whenever people just grab my phone and scroll through my photos without telling me. It's my own personal device, I use it to take tons of stupid selfie photos or private photos with my bf or whatever else I need, and so it's embarrassing to me and it seems unfair to me because that's something I would never do to anyone if I saw their phone sitting around. A big part of it is a respect thing to me, because I am so open and yielding all the time so I feel like I should be treated well for it rather than like a doormat. How would you feel if someone read your diary, or wanted to read your mind? Everyone has a right to have their own space to be themselves and record their own experiences and lives for keepsake without the interference of others, and it's up to one another to uphold that and respect it. If you see your SO's wallet or phone lying around when he/she's away, don't look through it. If your SO leaves something logged in, avert your attention. Even if you feel that you have a reason for doing it or that you cannot trust them, doing something wrong in hopes of making a right won't help your relationship; instead, your relationship will be tied in your mind to the disintegration of your own integrity and be basked in an even more negative light.
