opting-out is not OK via the GDPR. Only Opt-In is allowed or at least that's my reading

GDRP section 32

Consent should be given by a clear affirmative act establishing a freely given, specific, informed and unambiguous indication of the data subject's agreement to the processing of personal data relating to him or her, such as by a written statement, including by electronic means, or an oral statement. This could include ticking a box when visiting an internet website, choosing technical settings for information society services or another statement or conduct which clearly indicates in this context the data subject's acceptance of the proposed processing of his or her personal data. Silence, pre-ticked boxes or inactivity should not therefore constitute consent. Consent should cover all processing activities carried out for the same purpose or purposes. When the processing has multiple purposes, consent should be given for all of them. If the data subject's consent is to be given following a request by electronic means, the request must be clear, concise and not unnecessarily disruptive to the use of the service for which it is provided.

https://eur-lex.europa.eu/legal-content/EN/TXT/?qid=15323486...

Am I mis-understanding?

You are correct, however this is for when consent is relied upon as the legal basis for processing.

My guess is that they are using provision of service as the legal basis for processing, whilst relying upon the "public interest" clause in the ToS to justify the sub-processing by the third party.

That doesn't work, you need to have a legal basis for all processing. It's hard to argue that operating the service requires this sort of research, so you need another basis.

There's some public interest exceptions, but from my knowledge it's not established that stuff like this would work under it.

Yes, you are correct. I think it would be extremely difficult to justify that this kind of processing was necessary for the provision of service.

It seems to me that an organisation the size of Dropbox would have a fairly watertight justification. However if the legal basis for processing is neither consent nor provision of service, then they must have done a pretty good job of obfuscating all PII (as the article says "...we and Dropbox employees could view no personally identifiable information.". If this is the case then this sharing of information may not even be in-scope of GDPR.

I'm not sure if the public interest exceptions would be a safe route to go down. The EU has made it clear that, like 'Legitimate Interest', the get-out-of-jail-free justification is going to be highly scrutinised.

EDIT: I have just seen that the article has been edited to say that the anonymisation and aggregation was carried out by Dropbox before being transferred to the third party, which kind of kills the discussion.

They could be relying on the "public interest" part of their TOS, in which case they'd possibly argue that this processing was necessary as part of the provision of service, and therefore wouldn't require any further consent from the user.

For the record: I'm not suggesting that what they did was ok, just trying to think about it from a GDPR perspective. Anonymising account information is great and all, but how can you be sure you've obfuscated all PII from information saved to file storage, unless you audit all that information - which in and of itself seems ropey from a data protection point of view.

Why do you belive that the work under discussion was performend in the interest of the public?

It seems hardly necessary to share data with HBR so that Dropbox can offer file-sharing services...

Based on my reading here: https://ico.org.uk/for-organisations/guide-to-the-general-da... this does not apply.

So it looks as though the article has been edited to say the anonymisation and aggregation was carried out before being transferred to a third party, which craps on our discussion a bit.

However, to answer your question anyway - I don't believe you could justify the work as being in the public interest. I think it would be an extremely tenuous link and I think you'd be a fool to try and rely on something as flimsy as public interest if you're not a government body, or processing data on behalf of one.

I suppose I was taking a stab at understanding what their thinking was to see if anyone else could provide me with something which I had not considered.