Your brain my not remember the phone numbers, but it contains the location of (or the pointers to) the object that contains the phone numbers.

Sort of reminds me of the "extended mind thesis"

https://en.wikipedia.org/wiki/Extended_mind_thesis

Yeah, I've noticed that I remember a lot more information these days as... external references? Breadcrumbs? Like, I have no idea what that person's called but I know I got an email from them last Thursday so I can look it up if I need to. Or I don't know the exact phrasing of a quote but I know the exact search term I'd use to find it on the web.

Now, what happens when, say, memories of conversations turn into pointers to chat logs that are stored on the central server, where they can be modified, deleted, or your access taken away by the service or nowadays often by the other party?

I automatically backup all of my tweets to a google sheet that I then download periodically. I don't necessarily do it for the reason that you gave, but that's definitely a reason to to something like this.

We will be left with worthless dangling pointers to our memories.

Extended mind... interesting, but also seems untestable/in the realm of pseudo-science.

But I'll bet you know 20 passwords, or more. That fundamental skill is not lost. You're just not getting any phone number practice anymore. You're getting password practice all the time, I'll bet.

Unless you use a password manager and make every one unique and random.

Strong disagree. I don't remember passwords like I remembered phone numbers. Perhaps because I don't say them out loud, hand write them, and lunch them on a tactile keyboard frequently

Phone numbers, at least in the US, were much simpler 15+ years ago. Most people had a number starting with an area-code + first-3, out of say, 5-10 possible combinations.

EG, 123-444, 123-323, 123-789, 555-121. So, you really needed to remember the prefix and the last 4. There were exceptions, but most of your circle lived within this finite space of telephone numbers.

I don't even know my _own_ phone number at the moment. I got a new one weeks ago, but I just copy and paste it now when I nee d to send it to someone else. It feels odd realizing that I don't remember exact things as much anymore, because I can just look it up or forward them without having to process them.