Today's Internet is very dependent on undersea (submarine) cables that link various parts of the world together. We can seamlessly link between web sites in various countries only because these cables exist. Less obvious, but economically perhaps even more importantly, these cables enable many other kinds of communications traffic: email, voice phone, fax, instant messaging, and much, much more. They are, these days, vital conduits of economic activity – it's hard to imagine any kind of business that isn't dependent on them.
These cables (see diagram at right) are the most concentrated information conduits in the world. When one of them breaks, the impact is large and immediate. In some cases around the world, a single submarine cable is the only high-bandwidth link between some region and the rest of the world. When one of those links breaks, large numbers of people are sawed off from the rest of the world – no web, no email, no phones, just ... crickets.