What is 'network consensus'? It certainly isn't giving everyone a vote as to whether they think the rollback is a good idea or not. Instead, it's connected people wielding influence.
So can random people who agree with each other completely control everything that happens with the currency? So if there is a company who they dislike can they just decide that they have no money?
Majority of ethereum holders would want to rollback. That is consensus. If they don't hard fork they can keep running an old node. What is the problem?
The incentive here isn't to pick the side of the fork you agree with; it's to pick the side of the fork you believe will win. So you can't really say that the rollback side winning means that most miners agreed with the rollback - rather it means that most miners thought the rollback side would win. There's a strong element of "self-fulfilling prophesy" here.
Isn't that basically measuring which side has more hashing power? It's not obvious to me why that necessarily represents "the majority of ethereum holders". Or am I missing a mechanism?
The hashing power is the voting power. Since it is not obvious how one could even define what "the majority of ethereum holders" even means (and who says that every ethereum holder who is a physical person has to have the same voting power? If this were the case one would simply split your ethereum "account" into many who are hold by stooges).
It has been proven impossible to reach full consensus at scale in a fully decentralized, asynchronous system (the FLP theorem).
So, in computer science terms, consensus algorithms are about approximating distributed consensus in the face of benign and malicious threats or communication failures, which devolves to "quorum / majority" pretty quickly in a crisis.
After the crisis, some kind of compensation, reconciliation or excommunication has to happen with the portion that disagreed.
So that means if you are against majority thought you are shit out of luck. Just think of any time when majority consensus hasn't been the optimal solution.
If you believe that there is a better way to find a consensus in a distributed system than majority you are free to implement a system based on it. I consider it as quite plausible that such a system exists, but cannot even imagine how it might look like.
There is a better way but it unfortunately requires the system to have an understanding of what the decision is about - in other words, no longer decoupling the mechanics of the decision from the meaning of the decision.
A distributed system can easily make a majority decision that is unwise, like if the votes are based off of bad information. But if the different options of the decision could be formalized and checked/proven as part of the decision making process, based off of axioms and values that participants all agree on, then perhaps the most rational decision could be selected even if it's not what the majority was initially in favor of.
