I'm not sure what would happen to the NYSE if there were a two-day blackout in New York. I imagine that they'd probably have to shut down. I read a book recently that might be of some interest to Risks readers, as it addresses the problems of centralized data transmission and storage to some extent. The point was made that the seizure of the uplink could easily have resulted in a major collapse of the world's interlinked financial systems, if the data flowing through the link were to be cut off or corrupted. There have been plenty of examples in the past of the problems that can occur when a person's votes are not kept secret.
Otherwise fraud is far too easy, with mystery ballots appearing out of nowhere.
But recall the earlier Phillipine election in which a local power failure downed the central ballot-counting computer, which upon reboot immediately finished the ballot counting. Somebody has to be trusted somewhere. There is a choice as to whom the trust must be given. The results of such exercises are for good reasons classified under national security directives. Readers Digest, however, which obviously has good connections, has published several articles during the last 5 years describing the threat from foreign intelligence services as well as from industrial espionage.