I won't believe it's a Firefly sim until there's a placable River Tam block. Get on it, sir.
As many have no doubt pointed out, there is not now and has never been anything that stops anyone from building their own TCP/IP-based network and only allowing trusted users/machines/sites to connect to that network. There is no inherent need to connect *anything* to the public Internet, much less an asset that contains confidential information.
The thing that bothers me most about this announcement is the clear implication that secret data *isn't* currently partitioned onto private networks at top-secret government agencies.
Somehow, I manage not to have sex, without the benefit of this amazing technology you describe...