The rule still applies, in private or not.
I got a nice surprise on FB today. I had a friend request from some girl I didn't know so I asked how we knew each other. She was friends with several of my friends, so it was possible that we had met and I had forgot.
Her reply was, "idk I just added you because you look cute in the pic"
e - e - e - e - EGO BOOST
Thank god for cropped pictures.
Unfortunately, I had to tell her I was married, and denied the friend request. Later, I was talking to my wife about it and asked if she knew her. My wife said she was younger and really nice, but was easy to get in bed with... :'(