Everyone is a stranger… almost everyone. This is a fact of life, but for this INTJ stranger is the tittle of every person that hasn’t earned my trust. So regardless of how long I interact with someone, if they haven’t earned my trust they are strangers. This is really important because the predominant idea is that long-term exposure to someone in a “friendly” environment or manner automatically means that there is trust obtained. For this INTJ, I don’t know about the rest, 10 + years of social interaction is not conducive to trust most of the time.
This is visible when people try to initiate physical contact with me. Just because we interact, it doesn’t mean that physical contact is welcomed. That has to be sown under certain contexts to be welcomed.
There are people that I have known for 15+ years and I still consider them strangers because I don’t trust them. I would much rather try telling a secret for the first time to someone that I have only interacted for a year but has earned my trust than someone that I have interacted for a decade who hasn’t earned my trust.
To this last point I have to say that I’m biased. Most of the people that I have known for more than a decade have screwed up in one way or another and therefore the bit of trust that existed have been severed. I have also stopped identifying with my past, and that includes a detachment from the people of my past even if I still interact with them to this day. It doesn’t help that I never learned to make transitions to relationships properly, so it’s easier to cut someone off than to transition the dynamic itself.
So most people are strangers because we haven’t met personally. Some are strangers because nothing else have been obtained other than the awareness of each other’s existence. Some are strangers because the interactions either haven’t led to the formation of trust or the trust formed have been severed by human error. A few are not strangers because even though the interactions have not lasted long trust has been intentionally formed and maintained.