Yes, by a consensus of miners, or by users choosing a new set of miners. The "main blockchain" is not a decision of the miners. It's a decision of the people. If everyone agrees that current miners are behaving badly in a proof-of-stake system, they can just choose new miners.
OK, I'll bite, with a serious, practical question -- how would I do that this week?
Please assume that I have 100 BTC at a particular address or small set of addresses, and I don't like the Chinese mining consortia.
How do I actually move my value to a new chain that 1) excludes those mining consortia, 2) preserves my stored value, and 3) preserves my ability to transact with any other valid BTC address? How can I get this done by next week?
As I stated elsewhere, this is impractical for Bitcoin because the value of the currency would tank. For applications like the one in this article that use general purpose blockchains, forking is very practical.
OK, so the fork would accomplish goal #1, but not #2 or #3. I can have my own brand new BTCv2, but it has no value, unless I can get the majority of other BTC people to come over, and if a serious movement starts, the value on both chains tanks and needs to be rebuilt by trust, and the assumption that no one else tries the same thing.
Even when the point of the chain is not to store value, but just data, it seems that we're already losing the ability to track all the old data. Sure I extract a set of the stuff I want and carry on with the new fork, but no one else comes along, their data is lost, so they don't come along. If all I care about is a close network of friends, or perhaps an internal company data store, then fine, but how does one cleanly tear off a chunk of a network that looks like the graph of FB or Twitter? Am I missing something here?
If you have a good reason to switch blockchains, the developers of the clients users actually use should have a good reason to support the switch. If you can't convince people to change, you're stuck with the status quo. That's just a fact of life, not a flaw of blockchains.
> Sure I extract a set of the stuff I want and carry on with the new fork, but no one else comes along, their data is lost, so they don't come along.
That's not how it works. When you fork, you typically bring the entire history with you. It's the new data after the fork that causes problems. If people don't switch or publish to both, you're stuck.
I love it when people say this shit. Ok, I'll just go fork Bitcoin. Unless I'm not a programmer. And I sure hope that somebody else follows me into my fork. Only a group of major (powerful) market players will have the ability to threaten to fork. And even then, they probably won't, for the exact reason you stated: a fracture in the currency would kill people's confidence in the currency and tank its value.
The majority of participants in the Bitcoin network? Or the majority of its computing power?
This is a major worrying part about Bitcoin. Would it be really that difficult for a nation-state level player to buy enough capacity on the network to take it over?
