A lot of Personal Data discussions veer into discussing Privacy, but to do so in a meaningful sense I think we need to define what it is in the digital domain.
We seem to be caught between two stools of thought on Privacy - either Privacy is dead (aka Mark Zuckerberg and more recent posts such as http://www.washingtonpost.com/blogs/innovations/wp/2015/02/11/privacy-is-following-chivalry-to-the-grave-heres-why-thats-a-good-thing/
) or the Go Dark movement. To me this seems to be looking at issues incorrectly because we haven't defined what Privacy is.
Specifically , being private doesn’t mean not sharing anything - it means being in control of what you share, to whom and when. For example, I am a private person, but I share sex with my wife, I share family issues within my family group, I share my finances with my financial advisor, I am happy for my supermarket to know what I buy. The point is that in the physical world I am largely (but never completely) in control of my privacy and that includes what I share and with whom.
So privacy does NOT mean no sharing. This is important as sharing is the grease to the future economy - combining different data sets that I share will enable radically new services and experiences that I have yet to even think of. Privacy equates to controlled sharing. There is a spectrum of sharing for data items: from items I keep solely to myself, to items I share with one or a few people and ask not to be shared further, to data I may share more widely and allow to be reshared, to data which I share with the world (either as me or in anonymised form).
I'd like to include "for what purpose" in the above definition of what privacy implies re control and to most people they would. If I disclose to a close friend a secret so I can get feedback for example, I do not expect that secret to be disclosed to others - it was only for the purpose of our conversation. However, I can't control my friend directly and he may tell others. In which case of course he has lost trust and I probably won't share with him again - or at least will share more carefully. This is of course the same in the digital world. If I share with you for a purpose and you use for another purpose then I am unlikely to want to share with you again.
So, I propose we define Digital Privacy as the "Ability to control your personal data, inc. who you share it with, when and for what purpose"
(Note: the dictionary defines Privacy as the "condition of being secret". In my digital privacy definition I propose this is equivalent to "being in control of who is in on the secret".
Any other suggestions?