I would love to see a follow up to that. From what I recall, the PRISM program they used in that study wasn't the only one of its kind, and anything from the 80s or earlier wasn't included. They also didn't make mention of any of the CIA's old projects from the 70s / 80s that get declassified every few years. I wonder how much those would skew the results.
The paper is definitely a worthwhile read; it would be a fun exercise to go through other historical examples of whistleblowing and unmasked conspiracies (e.g. the panama papers, Chelsea Manning's wikileaks disclosures, MKUltra, &c) and see how well the authors' parameter estimates hold up.
[0] https://journals.plos.org/plosone/article?id=10.1371/journal...