@kev@thenewoil super stuff. I've made the link to herd immunity in my discussions with folks too, it's a lovely but subtle point.
I also think there's a parallel to draw with being good neighbours. Most folks I speak to think there's value to be good *physical* neighbours, and that this has declined in the last decade or so. I think we also need to consider what it means to be good *digital* neighbours. The "nothing to hide" view is, as you also conclude, selfish in this way.