Yes, these anarchies proofed that it works but I still think they had a great flaw. They still made the mistake to act territorial. They assumed it would be needed to free a territory to build an anarchist society but territories are easy to attack for authoritarians because they are always limited to specific regions. It's unfortunately very easy to destroy a region and to end territorial anarchies if you have enough weapons and a big army like the authoritarians almost always did.
But if anarchists would instead create a global decentralized network not bound to specific territories and bypass the borders set by the nation-states authoritarians would have far greater problems to destroy them. A global decentralized network can't be shutdown so easily by authoritarians and today we even have the tools to create something like that.
Tools like the decentralized HTTP-alternative IPFS and the decentralized Steem-Blockchain. Tools like generally all free (as in "not bound to any nation-state or other central institution") cryptocurrencies whose usability in theory isn't bound to the approval of nation-states.
But the main problems of today are the currently not so wide spread adoption of these tools and the fact that most people unfortunately still believe in the absolute unquestionable authority of nation-states like many believe religions.
That's the reason why many people f.e. still panic when f.e. rumors spread that the nation-states of South Korea and China would possibly ban crypto-currencies. Most people unfortunately still fear the authority of nation-states although it is, like all normative structures humanity ever created, entirely faith-based.
Only as long as people believe in the authority of a nation-state the nation-state exists. If the majority of people would stop believing in the authority of a nation-state it would sooner or later cease to exist.
RE: No Gods No Masters - A history of anarchism showing that it works.