The Belmont Club on 'Dark Networks'

First off, let me say that the Belmont Club is a very worthwhile blog to bookmark. Wretchard's posts are always insightful and interesting. His latest is no exception, here's a taste, but I recommend reading the whole thing:

John Robb took at look at the September 11 network and analyzed its characteristics. The Mohammed Atta network had evolved under Darwinian pressure until it reached the form best suited for its purpose: to conduct strategic attacks against the United States of America. Robb concludes that a cell of 70 persons will answer to the purpose, yet be sparse enough to allow its members to remain in relative isolation. For example, no one member of Atta's cell knew more than five others. Moreover, the average distance between any two members was more than four persons. Crucially, but not surprisingly, this disconnected network of plotters maintained coherence by relying on a support infrastructure -- probably communications posts, safe houses, couriers -- to keep themselves from unraveling. Because security comes at a price in performance and flexibility, Robb arrives at an astounding conjecture: you can have small, operationally secure terrorist groups, but you can't have large, operationally secure cells without a state sponsor.

Yet another piece of evidence for why we need to End States Who Sponsor Terrorism.