I agree that ISPs are a problem, but it's possible to build a reasonably blockproof service with a doze of p2p darknet and reliance on common transport protocol

I agree that ISPs are a problem, but it's possible to build a reasonably blockproof service with a doze of p2p darknet and reliance on common transport protocol (read: https). They would, essentially, have to find every node on the network and block them. Or perform very expensive traffic analysis, which can be defended against by designing normal protocol traffic to look very much like normal web traffic. As always, adoption is going to be poor because even among geeks it's rare for one to deeply care about privacy & anonymity let alone lift a pinky for it. Unfortunately, the worst threat is a legal one: just offer punishment for anyone who is found guilty of participating in such a network.