We don't even have a word for it - "public-ness" - as opposed to privacy.
I never know quite what to make of Jeff Jarvis. And considering the publicity blitz around Public Parts I'm unsure whether to post a public review. But that's the point. Unlike Clay Shirky's books, which lay it all out for you, Jarvis's writing makes you work for the underlying conclusion.
Although I find Jarvis' style sometimes grates against the content, there is real value here - for example the chapters on the history of public discourse and the bibliography. The later chapters on ethics challenging knee jerk reactions to open-ness are also a must read if you have a significant online profile.
In spite of this, ultimately, I came away with the feeling that Public Parts is a book which asks the right questions but doesn't know the answers. Possibly because there is no answer, unless we each arrive at our own. Which is, I suppose, a recommendation to read it.