It's possible in obe's but I haven't been able to do it yet - nobody knows how to have an OBE. In certain dreams there's been times where I've realized I was dreaming and tried talking to people to find out if they were real or not. There were a couple occasions where I was given names and addresses but when I woke up I forgot them and it would be a little strange trying to contact the person anyway.
I've been able to witness people in the physical while I was out of body and I even talked briefly with my dead grandmother about a year ago. Part of that conversation was about my dad who was sleeping in the chair of his home at the time so I had both things there - physical and spirit contact with family members. I have some friends who have told me if I ever get out of body and think of it to come visit them and tell them the next day what they were doing. I really don't want to "fly" into anything personal but I might try it one day.
Dreams & OBE's Letter 1 - How do you project from sleep paralysis?
Learn to Astral Travel - More Techniques on Astral Projection