View the businesses of the world as a large set of nodes interconnected by the business they do with other nodes. Some nodes will have tens of connections, some will have hundreds; a few will have millions of connections.

This type of network is often referred to as a scale-free network (cf. Albert-Laszlo Barabasi, Linked (2003)). This kind of network is particularly good at establishing contact between any two nodes with relatively few connections.

In order to visualise this, think of the hub-and-spoke systems that most airlines use. A few airports, like Heathrow in London, Hartsfield-Jackson in Atlanta, or Haneda in Tokyo are hubs and these airports all handle over 50 million passengers per annum. Compare that to say Esbjerg airport in southern Denmark with a throughput of less than 200,000 passengers per annum.

It is relatively easy to get from Esbjerg to Atlanta. You just fly to the nearest hub, London, and then board a direct flight to Atlanta: only two connections. Even if you had to get to another small airport in Georgia, you would only need three connections.

Another clear advantage the scale-free network has, is the resilience to random attacks. If you take out a few random airports in the world, hardly anyone will notice. There are still enough hubs to keep everybody connected. Similarly if a few businesses cease operations, it will not affect the global business network.

However, a scale-free network is very sensitive to a non-random attack. Say you targeted the hubs in such a network. Very soon the effects would be felt, and everyone would lose connectivity.

Banks are such super-nodes. The largest of them all carry millions of connections. If banks were taken out, very soon, the entire network would feel the effect, and the global business network would lose vital connectivity.

Faced with a loss of the most important super-hubs of the global business world, the governments could not just watch the banks drop out of the network. They all acted swiftly and decisively. Fortunately it looks like a financial meltdown was averted.

The government action to support the banks did not attack the root cause of the problem (which is not the topic of this article), so we may still see legion other effects of the underlying source of the banking crisis.