Yes, and that 'feature' of block chains is never really touted by blockchain supporters. Basically, if 51% of the network think you have too much money, they can just take it from you with no recourse available.

> Basically, if 51% of the network think you have too much money, they can just take it from you with no recourse available.

That's not how it works. Even if you had 99.99% of the hash rate, you still have to work within the rules of the chain, so a "give me your money" without a valid signature would still be rejected as invalid by every full node (and you just wasted your hashing power). What having 51% or more of the hash rate allows is a double spend attack: you can undo recent transactions, so you can spend a coin twice.

But the rules of the chain can be changed. If for instance 90% of the full nodes decide to change their software so that "give me your money" is now valid in some special circumstance X even without a valid signature, and that "give me your money" transaction is sent to the network, these 90% of the nodes will allow it to be added to the chain, and let the chain grow on top of it; while the other 10% will grow a separate chain on top of the last block without the "give me your money" transaction. Soon, each side has an incompatible view of which transactions are in the blockchain; this is called a "hard fork". And if the minority side is small enough, it will no longer matter if they still say you have your money, since everyone else you want to transact with will say you don't.

That's what blockchain proponents tend to omit: the blockchain is a social construct. Its rules are fixed as long as the majority of participants want them to be. When they decide to change the rules, like that time when the Bitcoin developers fixed a database bug which changed the validity of some blocks, the rules will change. Even retroactively.

It seems to me that large blockchains^ are some of the most stable social structures in existence. The rules of Bitcoin have been in place for 8 years with only minor modifications, despite huge sums of money passing through the system.

This compares very favourably with other social structures, such as nation states, especially 8 year old nation states.

^ Large as in Bitcoin and Ethereum, smaller networks are much easier to manipulate.

> It seems to me that large blockchains^ are some of the most stable social structures in existence. The rules of Bitcoin have been in place for 8 years

Indeed. Makes the Swiss federation and the King James Bible look quaint doesn't it.

This is a nice illustration that all property in general is a social construct: you only truly own something if the rest of the society agrees that you do. Blockchain is one particular way to set the rules, but our regular property laws are not any different in principle.

Yes. This was true before and after the hard fork. Seems like common sense to me, but I guess it's a good thing that the hard fork happened because it educated people that this is possible.