I want to highlight some points in response to your question and according to my best knowledge. Anyhow to give a more appropriate answer, need your question more specific.
In both cases
1) The risk factor remains everywhere. Even if something has 0.1 percent chance of bad happening, it might happen... “Risk theory”
2) Facebook is a huge company with large research and development sector. Surely, they have appropriate arrangement of data loss recoveries and to prevent hackers to wipe out their data.
3) Every process take some time so if such kind of activity starts happening, their immune system will detect the anomalies and take appropriate actions before a huge loss happens.
4) Even scrapping Facebook public data for research purpose requires proper legal permissions. They have checks for such activities.