After the Cambridge Analytica news broke, I thought about writing an amnesiac evil quiz app that did all the CA stuff but then once the user was done, it told them exactly what it did as a way to educate people as to what was possible (and forgot everything it learned once the point was made). This way the evilness is restricted to the person who owns the data (and thus isn't really evil).

I do think there's potential in something along these lines, but I agree with child post that it would need to be done carefully so as not to cause collateral damage. The other question in my mind is how to market it such that people get their friends using it and thus spread the word rather than panicking and reporting it.

So the data is out there and nefarious people are going to be nefarious... but I'd be concerned that such an offering would lower the barrier to entry enough that terrible neighbors might blackmail each over by finding such information. I think a more reasonable approach might be to build up such a service behind a auth lock, execute it for yourself and a journalist and send those two reports and the tool to the journalist.