Fact: the sole block chain being made by a few data centers = bitcoin centralized at layer 0.  Whether the network copies that on many proxies, or everyone goes and fetches the original, doesn't change the decentralization.

Decentralization is not distributivity.   Decentralization is "power of decision".  Distributivity is "many proxies".  Facebook is entirely centralized on its CEO.  If Mark Zuckerberg decides on a strategy, that will be what Facebook will do.  But Facebook is very highly distributed.  It has thousands or more nodes throughout the world and a very distributed network.

Bitcoin's decision power resides entirely in the hands of those who make the unique block chain.  Hence, if there are only a few data centres making these decisions, this is where the power resides.  If bitcoin's network has thousands of full nodes, it has high distributivity, like Facebook.  

In other words, the number of full nodes that hold an exact copy of whatever the miners have produced, does zilch to the decision power, but adds to the distributivity of the network, making it resistant to internet failures, data centre overloads, DDoS etc.... But it doesn't help in decentralization, because decision power is only in the hands of those who make the unique block chain.

Proof.  Suppose that bitcoin has 1 million full nodes, and only one miner, that has 99% of the hash rate (say, the Chinese government) even though we believe that there are 20 different mining pools.  Tell me what happens if the full nodes decide to implement, say, segwit, and the Chinese government switches to 20 MB blocks.


You cannot take action if the only chain out there doesn't correspond to what you would like.  The only thing that happens is that your full node stops syncing.