Global Interconnectedness

A study by researchers at the Swiss Federal Institute of Technology found that 147 companies form the core of the global corporate system and control around 40% of the wealth:

http://www.newscientist.com/article/mg21228354.500-revealed--the-capitalist-network-that-runs-the-world.html

The biggest risk is actually the instability created by so much concentration – contagion effects can lead to  financial meltdowns on a global scale rather easily in such settings.

The full paper can be found here:

http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.5728v2.pdf