So many online services use the proximity of phones to determine things like related persons and related accounts. Facebook is notorious for this. In one building I lived at Facebook would constantly show me the names of everyone coming in and out as "You might know this person" even though I had no idea who they were.
I have no idea how this isn’t illegal. I’ve experienced the same horrifying loss of anonymity before. People I met long ago and definitely do not want knowing my real name showing up as Instagram suggested friends.
Or people who stay next door at an Airbnb and I had a quick chat with in person, like I didn't give them any contact information nor did they give me theirs so how ...
