The whole idea is a privacy minefield, so it would have to be very carefully designed and implemented, of course making it opt-in. But still, should we even pursue this idea?
So that, for example, even if I met someone just briefly, they can still later see the contact information that I am willing to provide.
Wouldn’t that make it much easier to connect with people who live close to you?
Are there any relevant projects or ideas that already exist?
No. This would be a mess security-wise.
Theoretically yes, but actually nothing ever happens. I have seen an app’s API disclose its 6 million user profiles, with name, gender, age (minor included), hobbies, bio, and exact location. Technical people know about this security breach, but it was never fixed and no user was ever endangered