The only real one I can remember off the top of my head, where facebook giving access to data didnt turn out to be userbase hands over data on themselves and friend, was the Netflix and some others getting access to private messages. And even there, it wasnt nefarious, it was facebook trying to extend people features, like being able to send their friends spotify songs.

https://www.theverge.com/2018/12/18/18147616/facebook-user-d...

To use most user-data-serving Facebook APIs, you need both authorization from the user whose data you’re reading and approval from Facebook itself for your app. Facebook has been accused of bad behavior when approving and denying apps, but they haven’t (as far has been reported) released any APIs to get user data without first asking the user.

This is true, but I doubt most users understood exactly what they handed over when they clicked "log in with Facebook".

at least there's always a tldr (you know what exactly you are handing over in a few bullet points), especially when you think of all the contracts/fine prints/ToS you accept in life..