Basically, this now gives the office of president the ability to turn off the Internet. Like, completely. Oh yeah, and it's already been passed without the pesky public weigh-in. Thank you representative democracy!

The security reasons for this are somewhat vaguely defined too, but in the end what raises the alarm for me is the fundamental nature of the Internet, which is information: information is never bad in and of itself, only its applications.
So what are they afraid of really?
from http://www.campaignforliberty.com/blog/36327/
The neo-conservative Senator Joe Lieberman has introduced a bill to give Obama power to shut down the Internet by declaring a national emergency.
S3480, the "Protecting Cyberspace as a National Asset Act," not only allows the President to seize and shut down large parts of the Internet any time he wants to declare a "national cyber emergency," but permits the President to shut down the Internet across the entire planet.
As antiwar.com notes, "the bill amounts to a remarkable claim of presidential power, claiming a large portion of the global economy as a specific asset of the United States and further claiming the right to nationalize or destroy it in whole or part on a whim. The news may be disquieting enough for Americans faced with this sort of power grab from their own government, but for foreigners the idea that another nation can commandeer the Internet, cut them off from it, or render it unusable is totally shocking, and not surprisingly, a source of no small consternation.
"When reading through the bill, one can't notice how frankly it claims such enormous powers, or imagine how shocked the entire planet would be if Sen. Lieberman proposed the same measures without adding the prefix "cyber" to every few words. Couching it as a technical matter, with the usual technical ignorance of a Congressman thrown in for good measure, is a way to hide exactly how sweeping the new powers would truly be."