In _Depletion and Abundance_ I spend a lot of time talking about the ways that the informal economy is actually more robust in some ways than the formal economy, and the ways that informal economy activity can strengthen our home economies. I argue that in the Developed world, the informal economy is hidden or "housewifized" out of existance - we think of it as a small portion of our life, and not significant, but in fact, the informal economy is enormous and critical.
If you haven't read Robert Neuwirth's _Stealth of Nations_, you should, for a much more in-depth analysis of the role of the informal economy. Check out his Fresh Air Interview here.
Definitely worth a read - a very, very important book!