Assuming reasonably equal resources and knowledge: two parties attempting to knock each other off the internet can result in only two outcomes: either they both get knocked off or neither does. The possibility of either party “winning” is essentially impossible. The Internet’s combination of network redundancy and ability to communicate with, and garner assistance from, sympathetic parties from around makes it nearly impossible to for one party to squash another. The only thing they can do is cut themselves off completely. I think of this is RMAD “Recoverable Mutually Assured Destruction” since they can turn it back on afterwards (unlike the nuclear MAD).
We are seeing this now in Iran. The government controls the connections, but can’t cut off the opposition without cutting themselves off. So we are seeing outside parties providing proxies and passing along messages (see http://twitter.com/#search?q=%23Iranelection).
This is all intuitively clear and long predicted, but I think this is the first time we are really seeing it in action.