Facebook built it’s business on sharing information. Facebook itself has before acknowledged that without their ability to share they can’t have the business model that they do. I don’t think that a privacy-first model would have allowed them to exists (which may be a good thing to some).
That said, Facebook was of help to me (actually someone else) today. A non-USA citizen with authorization to work here lost a bag to theft. Walking from my hotel to a breakfast spot I found his USA issued ID and authorization to be here for work which had been in the bag. Looking through several social media sites I was eventually able to find him under a slightly different name in Facebook and managed to get this ID on it’s way back to him. His settings were more private on some other sites and I had no way to contact him through them. But thanks to one of his friends that had once tweeted about him I was able to find the name under which he had his Facebook account. I don’t know the ramifications about not having the item returned, but he expressed a lot of anxiety over not having it anymore.