The issue there was collection of massive amounts of public data by Facebook. Open data APIs can be used to build nice things, if the data isn't user information.
The app "This is your digital life" let people do a psychological profile linked to their FB profile. The Open Graph API then gave Cambridge Analytica to (some of) their friend's data as well,
https://www.cnbc.com/2018/04/10/facebook-cambridge-analytica...
https://medium.com/tow-center/the-graph-api-key-points-in-th...
Turns out that wasn't a great idea. Disappointing because it's what I wanted too.