Contact tracing: individual privacy matters. But there's a collective dimension to privacy too. Relational data. Aggregate data that are more than the sum of their parts. Here's one way to think about it.

Privacy is a shield that protects other values. Two are freedom and sovereignty. Each has ind'l and collective varieties. There's my freedom to live without interference (etc), and my claim to sovereignty over the things I make and do—that they not be used without authorisation

But there's also our freedom to set the terms of our shared existence, as a collective. And their's our sovereignty, over our collective resources (even our 'name'), that they not be used without authorisation.

These apply to data too. We should care about individual privacy, because we care about individual freedom. We want to know that your data are secure, and shared only under terms that you can endorse.

But there are relational and emergent properties to large datasets. They are more than the sum of their parts. And those data, in aggregate, can further undermine individual freedom and sovereignty. And they can undermine the freedom and sovereignty of the group too.

So while it's important to know whether these contact tracing apps respect long-standing privacy principles around personally identifying information, it's not sufficient. Just as important is to figure out what this system will look like after it's been running for some time

What kind of data will be held? How could it potentially be used? What are the possible unintended consequences? For example, how can we ensure that the Apple/Google protocol will be properly sunsetted—will a year or more being 'bluetooth-tracked' inure us to it,

so that when the pandemic is over we tolerate the same methods in adtech? Individual consent can't help us in these cases.

There's a lot of good reading out there for those interested. Probably the best, to my mind, is https://nissenbaum.tech.cornell.edu/papers/BigDatasEndRun.pdf by @HNissenbaum and @s010n There's also a helpful collection on group privacy by @linnetelwin and @Floridi, and Bart Van Der Sloot here: https://linnettaylor.wordpress.com/2017/01/10/group-privacy-a-new-book-on-the-next-generation-of-privacy-problems/