A public block chain, regardless of encryption, is antithetical to privacy. No encryption lasts forever. To think otherwise is hubris. NO rollback, no delete

A public block chain, regardless of encryption, is antithetical to privacy. No encryption lasts forever. To think otherwise is hubris. NO rollback, no delete, no undo is a problem for the blockchain (as it stands today). It has uses, but these limitations make for interesting constraints that most problems dont fit into.