> The biggest problem is that most of the interesting private data is actually about relationships between multiple private individuals. If you're having a conversation with a friend on Whatsapp, is that conversation property of you, your friend, or do you each own your own messages? If it's a group conversation, is the whole conversation owned by all of the participants, or only parts of it?

To me, not addressing this one of the biggest flaws of the GDPR.

As a practical example: I've talked to numerous other banks, and with regards to data portability (article 20 GDPR), there is nothing even close to a consensus as to what you are allowed to give the customer with regards to his own transactions, because there are numerous parties involved.

It gets even worse: the text of the "right of access" (article 15 GDPR), in a wide interpretation, grants access to far more information than the data subject would otherwise have access to.

If person A and person B confidentially process data of C, is it really the intention of the GDPR to grant person C access to this confidential processing?