There was also Google Latitude way before that. I remember how excited my friends were to watch other friends move about the city. It did come in handy one time when a friend left his phone behind at a corner store and didn't realize until later.

If a friend is posting a person's location, they likely post other information about that person. The aggregate information could allow the assembly of a much more complete picture of a person than is possible by observing a person at a random juice bar.

For example: are they married? Do they live alone? Who are some of their friends? Where do they work? What do they do at work? Have they recently lost/found/experienced something interesting? These are the kinds of details that can enable social engineering in digital and physical spaces. It's likely easier to lure a person into a dangerous situation if you reference minute details from their personal life.

Sometimes the threat model is "has $10k in a bank account" or "is young & attractive" or "practices a religion I don't like" or "it's Tuesday."

It's not their data to share.

It's data entrusted to that specific person with the social contract to not share that data (assuming no permission for sharing was given). I would argue the same way if someone posted my full address online for example, you're breaking the social contract by sharing data I entrusted you with.

Perhaps they didn't tell their friend about that one abusive ex or an affair their having. Additionally in this case it is telling people that when this person is in a certain location they are having a bad day, possibly opening them up to harassment a scam or manipulation.

There are a lot of people that will use that information to their advantage, even if it is just for trolling.

For me, if I found out about a post like this I would stop any contact with the person effective immediately after informing them of not appreciating the post.

well in my particular example it's a juicebar she frequents when she's had a bad day. So, she probably lives or works in the neighborhood. And a detail I didn't share was that she was attractive (her icon on the map was her headshot). So someone could get it in their head to approach the person and know what she looks like, where she might be, and believe she needs cheering up

And it's NYC which has all sorts of people, many of which you may not want to be approached by.

If the juicebar gets tagged, then the people working there may start interacting with the friend in a way she may not appreciate.

Sending out life specifics, even if your not famous or have a stalker can be detrimental. And, it wasn't the friend's choice either. So, the original poster may loose a friend in exchange for likes on X.

First, I responded to examples of 23 and 29 year olds. Second, I pay for my adult children's phones and don't track their locations, but I would if they asked me. They have lost phones and mentioned that they should at least setup find-my-phone and give access to someone. I would let them track me, but I'm still using a flip phone.

Vehicle insurance and owner liability is a whole different topic. I prefer to have them hold title and therefore liability, even if I were to give them the money to purchase and insure.

As I responded below, I do pay but have never tracked. The point is if you want to be independent of a parent that does not respect your privacy, then pay for own cell plan.

this "weird control issue" is SOP for like any organization, anywhere.

if you have a corporate cell phone it's telling on you. they pay for it, they have the right to track and read anything your doing on it.