That's what bothers me for years now in the context of contacts on smartphones. Maybe I'm making a mistake when thinking about it, but - if I refuse to share my

That's what bothers me for years now in the context of contacts on smartphones. Maybe I'm making a mistake when thinking about it, but - if I refuse to share my contacts with let's say Instagram, but all of my friends share their contacts list which includes me, does it really matter if I decline to share or not? Another part which bothers me is that I have lots of different personalities online. On most sites I use different usernames, and I wonder if there will someday be an AI which can match all the different online profile to a single person, even if different username are being used etc.