He started a blog about his experiences at Valve [1], but stopped shortly after starting it. I was a bit disappointed, because the posts were very well written and insightful. I'd guess now he really has no time for it.
Yeah, perhaps it's sad but I'm more interested in the synthetic economic systems of a game than the macroeconomics of the world. Somehow the former is more honest (probably because one has all the data).
[1]: http://blogs.valvesoftware.com/economics/