And here lies the innovation of proof of work schemes, preventing one party from casting arbitrarily many votes by making votes expensive. This also is no innovation of Bitcoin, Bitcoin just put all the pieces together. But if you don't need pseudonymity and can know the involved parties there is no need for proof of work, i.e. you can easily replace mining with an identity verification process. And you get a system that is in some sense better because you remove the possibility to obtain more voting power by buying more hardware.
It doesn't work without that centralized arbiter because then you'd end up with situations where each party has their own separate list of other parties that they consider vetted, and this falls out of sync, and the blockchain completely falls apart as there is no longer consensus on whether any given block is valid or not.
I will agree that the banks can probably come up with a centralized arbiter that works for them, and thus they don't need blockchain technology, but that isn't a counter to my assertion that the blockchain's key innovation is that it allows decentralization in a way that was never before possible.
You could come up with something like the process when verifying a domain for a certificate, creating a special DNS entry or serving some specific content at a specific address. This doesn't really work because nobody stops you from registering arbitrarily many domains, it is just meant as an example that the process does not necessarily require a central authority.
But there is a hard problem here, who is a party and gets one vote? Could a bank just create ten shell companies and then obtain eleven votes? Bitcoin kind of sidesteps this problem by implicitly declaring you a separate party if you possess some mining hardware and weighs your voting power by the hash rate of your hardware.
So you are definitely right, Bitcoin achieves a degree of distribution that is probably really hard to do without a trusted central authority that has the power to decide who is a separate party and who is not.
If the number of parties is small you could maybe still do it in a distributed way with some manual work. If a new bank wants to join they broadcast a request, use something like the mentioned DNS record to prove that the request is genuine and then all existing parties have to manually decide whether to accept or reject the new party and cast a corresponding vote. But this obviously doesn't scale well.
There's a chicken-egg problem there that requires a central arbiter to bootstrap, but the central arbiter then immediately becomes powerless.
An immutable data store of data would be a new type of storage system the world has never seen before. Up until now, things stored in a database have always had a decent amount of probability they wouldn't stay there forever.
It would be nice to be able to pay a decent amount of stored value to keep some truths as universal truths, where the probability of losing those truths approaches zero. I think there are truths that are worth keeping around and ones that are not.
Figuring that bit out is the next hard thing.
That sounds like a very anonymous way of distributing messages. Bitcoin's anonymity is more like having an unregistered bank account whereas BB (before bitcoin) all bank accounts were registered in one way or another. You don't even need an 'account' to accept a payment, u just need a magic number, though there is arguably not a difference. I feel like you're talking about network layer anonymity and everyone else is trying to talk more basic protocol.
Real breakthrough of Nakamoto is devising a scheme where whole network is protected against Sybil attack. I.e. there is no need to don't trust or register parties who participate in the network.
All elements of Bitcoin, such as proof of work, crypto ledger, merkle trees, etc were already known. Nakamoto combined them in a way which solves an unsolved problem.
The blockchain elegantly solves a number of problems that had individual solutions, but does it in a way that is easy to repeat and extend while not having any obvious gaps.
And I actually think that last part (lightweight account creation) may be what the banks are after here. It allows them to obfuscate transactions on the wire by using one-time accounts so that other banks not involved in the transaction know who is transmitting what from looking at the blockchain -- while at the same time providing enough transparency and security that banks can independently validate transactions they were involved in.
If I were to file a lawsuit against you as an individual, or prosecute you as a government agency, then probably yes I could. First, I can probably simply compel you declare them during discovery. I will allege that you're engaging in fraud and money laundering as part of shielding your assets against a debt that you owe me (let's say). I will explain that you've purchased bitcoins on an exchange for the purpose of shielding and hiding your wealth. (You're declaring bankruptcy in order to get out of a debt.)
We'll discover how much you've transferred to the exchanges that you do business with by compelling you to declare it, or by subpoena. You're now in the position of proving what happened to that money, where it went, and demonstrating that it's not still an asset. Enough people have heard about bitcoin and Silk Road on the news that there's a good chance a judge will see this as shady behavior, especially if you're not cooperative in revealing information.
If you have purchased bitcoin mining hardware and mined the blocks yourself, then we'll probably find that out during deposition. I'll figure out how much hardware you have and what its estimated hashrate is. You can keep the actual bitcoin addresses secret from me, but the fact of the wealth created by them will not be secret from a court, and you'll have a steep hill to climb to keep the bitcoin addresses and the amounts you've earned secret without contempt of court. If you've transmitted nontrivial amounts of money that's obviously going to a bitcoin exchange, or left any trail of financial records of purchases of bitcoin mining hardware, or if you disclose by answering honestly during deposition, and refuse to explain what's happened to those coins, then it will be obvious to a court that you're engaged in black market activity, money laundering, or are shielding your assets. An honest citizen doesn't hide their bank account information and activity from a court in circumstances where it's relevant.
If you have left no connection whatsoever between your traditional identities like your bank accounts, and with your bitcoin identities (like through an exchange), then it will be harder, especially if you lie under oath and claim you don't have any. For example: maybe you got into bitcoin in the early days when you could mine on a PC. You held onto those coins for years and are now a bitcoin millionaire. You recently bought mining hardware in a server farm you've never seen with those coins anonymously, and you're now mining more coins. This you could probably keep secret. If there's been any conversion with USD without a lot of anonymity, then there's going to be an obvious trail that will show up in a civil or criminal investigation.
Now, to be fair, I cannot find this information out about you, you being an anonymous person I know nothing about over the Internet. However, I also have no cause to care. If I have any cause to care, like if we have business dealings, then I will have enough information to leverage this process against you. Furthermore, it's not like I can find out your bank account number or credit card number either. The point I'm making from this is that bitcoin is not more anonymous than those instruments unless you've gone really far down the opsec road, buying mining hardware in cash, and engaging in money laundering to keep these secrets, lying under oath, etc. But to be fair that is an advantage. If you buy bitcoins in cash, you can spend them online anonymously. I would not describe any of this as "trivial" necessarily, but at the same time, I also feel like if you and I were to get into any legal altercation involving finances and money, I could probably do it. Though you do retain the power to keep them secret by risking contempt of court.