How do the banks ensure that aren&#x27;t outmined? One of the key components of a blockchain is that no one mines more than half that chain.<p>If you have too many blockchains, then you split the miners between the chains and open the doors for a big player to come in and overwhelm the other miners on that chain.<p>I suppose you could somehow implement private blockchains where only those with the private key can participate, but I don&#x27;t know whether this has been done or not.