Just saying:
The entirety of the United States' infrastructure, from transport systems to electricity and water supply is connected to and controllable via remote access throught the internet.
Also, the People's Republic of China is the only country in the world whose army boasts a candid cyber warfare unit, which actively recruits members of the hacking community (who, despite the 7 year jail term if caught brazenly advertise on recruitment websites) thanks to the power of nationalism.
Russia also has set a precedent of internet-based attacks, following that removal of the bronze war memorial in Estonia; as at yet, cyber assaults are not covered by any of the Joint-Security arrangements in the world. DDos attacks and hacking hurt!
I'm not saying that having an emergency shut-off is the answer to this, but there is a definite threat, and it definitely needs a solution. Perhaps if there were more people who actually understood the intertubes in power, then we would have evolved a solution by now. And of course the idea of an "Internet Kill Switch" is retarded.