So here’s the truth and how it came to be that Mark Zuckerberg is currently on the stand testifying.
A developer/programmer using the API, upon given fast permissions by a user, would/could immediately gain access to that users friends list data which included the entire stack of data for all the friends, it was NOT limited.
The further truth is that there were developers with as many as 500M users and counting that NO ONE even knew who they were. One of them was actually named Boris and was believed to be Russian.
To go further, the CTO of Cambridge Analytica was the former CTO of the RNC up-until the 2016 election had completed. Now how does this factor exactly? Do the math. Was he in possession of the the data?
The testimony does not clearly describe the extent of the data flow. If you put data in the platform someone other than Facebook owns it. You should bet on it, accept it, and be dillegent in your efforts to defend yourself against attacks to credit and other.
A word about things like your birthday or SS#:
A birthday is used many places to cross-qualify your identity. You should NEVER use your real birth date on a social network or any website where the data is not absolutely secure (which is like every one). Unless it is a gov site where it is required, you should avoid using it.
Facebook CEO Mark Zuckerberg spent a second day answering questions from members of Congress on issues regarding user data collection and faced some harsh criticisms over his previous apologies and lack of action.