Egypt has activated its own internet kill switch. This was a desperate act, but the consequences of using such a contingency plan would be even more dire. I don't have to tell anyone reading this that much of the US economy depends on the Internet. If the Internet went offline tommorrow, many Americans would be unable to make phone calls, and thus would not have access to emergency services such as police, ambulances, and firefighters. Whatever the reasons for activating the kill switch, there will be panic and conspiracy theories galore. It could very well cause more civil unrest than it prevents.
Proponents of a US kill switch claim that it could be to prevent a cyberattack. Talk about destroying the village in order to save it. Thousands of IT departments ewploying various security measures can do a better job of protecting themselves than a single giant bureaucracy.