3-minute 2006 TED talk by Stewart Brand here. From one of the slides in the talk:
This is interesting to think about as an example of a granular, bottom-up solution to something that is usually presented as a huge, monolithic problem. It is also fascinating to think about how much less economic friction there is in such a society: the talk claims that unemployment is 0% -- everyone works. What are such cities giving up for this lack of friction (in the form of regulation, taxation, and things like school attendance laws)? What is the risk exposure of a typical family? How (and how well) are disputes settled?
2006 Newsweek article.
Robert Neuwirth is a researcher on this subject, with a book ("Shadow Cities: A Billion Squatters, A New Urban World") and blog. These were mentioned on BoingBoing in 2005, where Cory Doctorow discusses some parallels between squatting and "copyfight."