PSA, if someone asks you for contact info (e.g. a phone number) of someone you know, the correct response is "I can't give that to you, but I can give them yours".

It's efficient and adds no round-trips, it's privacy friendly, it's non-awkward and it's social engineering resistant. It's a universally good rule.

And the corollary, of course: Don't ask someone for another person's contact info - ask them to pass on yours.

It's frustrating that not everyone knows and does this. Like, even in my peer group, where I'd expect baseline awareness of privacy issues, a friend recently gave my number to another friend without asking.
@Merovius yeah, I've had to politely decline and offer to pass messages in the past: I know you know each other but that's not a reason.
Besides, I'm not sure how up-to-date my contact list is now, but my address list is sacred and I'd only divulge if I thought someone were in danger of harming themselves. Our holiday card list is upwards of 170 people, some.of.which would put their families at risk

@Merovius

were this better established and respected, "Give ThisApplication access to Contacts" would never have gotten off the ground.

Yet here we are, where it's industrialized, personal data strip-mining, matter-of-course.