I'm old enough to have lived with a phone number published and not have to worry about it. Then came the telemarketers. Still, long distance calls were expensive and such calls were relatively rare. Next, long distance calling became effectively free and telemarketing calls were becoming frequent. However, it was still only a dumb phone - so nothing to worry about. Then, smart phones came along, storing personal information and being potentially vulnerable to threats. They were also used for authentication. But hey, not to worry, since it's just like before: everybody used to be in the phone book ...

First they came for the Landlines. I was not a landline, so I did not speak up...

It's not the digits of the phone number or the name of your street that are sensitive. It's the way they connect with all other aspects of your life.

The white pages never told me who was friends with whom. Or what everybody's sexual preferences were. Or any other data except their name and phone number.

One FB notices that you exist, they build a profile on you that includes much more than these two pieces of info. OP was trying to avoid being "noticed" by FB in the first place, to prevent the profile being assembled.

Similarly it took effort to look up random numbers in phone books. Few if any were ever printed in a way that made it easy to to from number to name, only name to number.

> Few if any were ever printed in a way that made it easy to to from number to name

Law enforcement, most libraries and other phone companies always had access to public printed reverse number phone books in the late 1980-1990's.

Point taken, not familiar any libraries that was large enough to have such items shelved.

> I don't really understand the motivation trying to keep one's phone number or address secret.

Random people/companies calling you at home, harassment, generally people on the internet being less than civil especially if you are a woman.

Earlier, phone numbers were listed. Currently, phone numbers and the frequency of interaction between these phone numbers are recorded by Facebook. The situation is not similar to a simple yellow page directory. It's basically a yellow page directory which real time updates - Bob called Alice 5 times and sent 10 messages.

Previously I would agree with you but with more and more of our life moving online, the repurcussions of someone malicious having identifying information about you are grave. For instance, you could be a target of a 2FA hack based on a cell phone number spoof.

That's just more incentive for companies to stop doing insecure 2FA over mobile networks.

When uploading your contacts the secret isn't your or their phone number. It's the relationships. The phone book never listed all of your friends and family.

Look beyond the face value and see the implication

Not everyone who has a mobile or is online grew up in that time period so the perspective is foreign.