If I had walked into a logged in computer I would automatically log off. I can't lie I would go through  the stuff but I wouldn't expose them in any kind of way. The reason I would log off because I know if I would have made a mistake and kept my computer logged on I would want somebody to do the same for me. I most definitely wouldn't stay on the other person's account like I said before I would look through the stuff because i'm nosey but I wouldn't hack their account.