It is interesting and useful as a concept. You cannot really improve anything if you cannot measure it accurately, and so data gathering and analysis can certainly be extremely useful.
However, I don't see much value in just collecting these digital signals like typing and email. Contrary to the title of the post, it is very impersonal. It is just email, really, and even for a serious tech head like Wolfram, that is surely a tiny part of his life.
I also am one of those people with a huge email archive going back decades, and it is fun to play with. Certainly it is fun to find the first emails you sent to someone from ages ago. I also saved all of my old engineering notebooks, and it is great to go back and see things from the early days of QuickTime or notes from the very first time I saw a Mac Laptop - that sort of stuff.
But I think it would be great if I could keep a detailed record of the things that I really care about. For example - I would like to know how much exercise I am actually doing, so I can see if I am really taking the stairs more. I would like to know how much time I spent in the car, so I could make more accurate decisions about the cost of living far from work. I would like to know how many new people I am meeting every week, so I can see if I am becoming more or less social. I would like to know when new topics are trending for me, so I can make sure I am continuing to expand my interests. I would like to monitor how much time I am spending with friends and family as opposed to just work and workmates. I would like to know how many times I gave a sarcastic answer to a question to make sure I am not becoming a dick. Now that I have a Kindle, I can't tell if I am reading more or fewer books than I used to. Am I really watching less TV because I play more video games, or am I keeping that constant and stealing video game time from other non-screen activities? These are just a few examples. No doubt you have your own list.
The point is that if you care about acting a certain way, it is super useful to measure it. You can measure all of the things I mentioned right now, but many of them are a huge pain. If technology could somehow make this easier, I would be all for it.
I just don't want FaceBook or Google to do it without asking me. :-)