The boundaries between public and private information systems

There is currently a push in congress to pass a cybersecurity bill, which opponents claim will give the government the power to shutdown private infrastructure that is deemed "critical infrastructure" to the United States:

Civil libertarians slam McCain cybersecurity bill

In the spirit of setting up boundaries, it seems that giving any type of access to an overarching governing body would allow a single point of failure for the security of all of the nations infrastructure. I am interested in discussing the pros and cons of this type of security policy as it would affect public and private sector security programs.