>They are not write only.
I guess you can delete data from a blockchain by having a rollback.
The etherium blockchain also is much more than a "block chain". But it is still very much a solution in search of a usecase.
Digital money is the only area where a blockchain is a sensible choice from a technical point of view, that I know of. Although I am entirely unconvinced that bitcoin or etherium actually are even close to a viable interpretation of digital money. Say what you want about paypal, it isn't distributing my payment details publically.
The etherium blockchain also is much more than a "block chain". But it is still very much a solution in search of a usecase.
Digital money is the only area where a blockchain is a sensible choice from a technical point of view, that I know of. Although I am entirely unconvinced that bitcoin or etherium actually are even close to a viable interpretation of digital money. Say what you want about paypal, it isn't distributing my payment details publically.