I don't particularly worry about my individual privacy, or care about securing my things. If someone managed to get a hold of my email, I wouldn't be very put out. I don't encrypt my hard drives, or even back anything up. My lack of security and privacy hygiene, however, doesn't extend to my work stuff. I care about maintaining the confidentiality and privacy of that stuff because it's part of a social contract (and I suppose also an employment contract) that I have with my work and my clients.
Instead of his diary example, what if he had asked his friend "Can I copy all of the emails off of your phone, or all the phone numbers in your addressbook?" Maybe they still wouldn't care, or maybe they'd now have to take into account the fact that all that data also involves other people, and maybe they wouldn't find it acceptable for you to give our their cell phone number to anybody who asks.
So much of the data that we accrue is increasingly more interconnected with other people. I feel like that's where we run into trouble, because there is no universal consensus around what's private and what isn't. We have rudimentary laws protecting the smallest subset of data which the government has decided should be considered private, but everything else is a value judgement for individuals (and is part of the current internet company land-grab).
I feel like his position is going to be harder and harder to maintain, as more and more of the "personal" data he's okay with sharing includes other people's data.