In Datomic, you are responsible for the contents on it, but this is the exactly the same for people writing to the blockchain. The notion that by organizing a group of profit motivated to validate transactions is really the same thing as a centralized organization. Look at the Chinese bitcoin miners. How many times have we forked? Now the forked bitcoin is forking!
Say you took out a mortgage on an open ledger (a PoW based blockchain ledger), BYOB. What happens when you get scammed? How do you reverse the transaction? What legal enforcement is there? Remember, you've said it yourself, the blockchain's supposed value comes from that nobody has full control of the database, but this is flawed thinking-the absence of authority does not make a ledger more trustable just because it's not in the control of anyone, which is false, bitcoin being a clear example of centralized ownership, or a perfect model of "rich miners getting richer".
Trust is not a simple matter of storing information, it's much more than that. It's based on human to human level trust, which blockchain industry has pretty much failed spectacularly with the vast majority of ICO pump-dump schemes.
