Not being able to access your windfall because you forgot your bitcoin password. The private key is cumbersome and looks something like this: E9873D79C6D87DC0FB6A5778633389F4453213303DA61F20BD67FC233AA33262. Protecting the private key is paramount—anyone who accesses it can transfer or spend the bitcoin, and transactions can’t be reversed or stopped. Typically, clients have a vague notion of their password already, and send Dave Bitcoin any possible words or characters they might have used. On the day of Mr. Murdoch’s birthday, Dave Bitcoin emailed saying that his password had been retrieved.

Source: Wall Street Journal December 19, 2017 16:38 UTC