TL;DR: they don't give a shit about privacy.

https://hbr.org/2018/07/a-study-of-thousands-of-dropbox-proj...

Quote:

> Dropbox gave us access to project-folder-related data, which Dropbox had aggregated and anonymized, for all the scientists using its platform over the period from May 2015 to May 2017 — a group that represented 1,000 university departments (from the top 100 universities and their Dropbox collaborators from other anonymized universities of any rank).

This was done without the consent of those involved.

Wired seems to cover the story: https://www.wired.com/story/dropbox-sharing-data-study-ethic...