Sometimes it seems as if everyone has bought into the hype: Industries as far-flung as real estate and diamond sales1 have embraced blockchain without entirely knowing what it is or how its most vaunted features might fail or have unintended consequences. Blockchain assures users that once information has been stored, it can never be deleted or falsified. This means that when people in finance, say, pore over the history of a transaction, they feel content in the knowledge that illegalities h...