It analyzes the stability of our global system is to look at it as a network: They used autonomous agents with heterogenous measures of fitness (diversity of goals/needs) to model an evolving network (similar to our economy or global trading/financial system). Unsurprisingly, they found as they scaled the connectivity of the network it became more fit. Simply, it allowed each of the agents in the system to better meet their goals for fitness (health, wealth, etc.). They also found that the network was also able to shrug off more small shocks than ever before (robustness increased). However, this general improvement in fitness and resistance to minor shocks came at a cost. The more highly connected the network became, the more prone it was to catastrophic failures/extinction events

Commentary by John Robb at http://globalguerrillas.typepad.com/globalguerrillas/2009/04/the-increasing-frequency-of-black-swans.html