Also, Bitcoin has an advantage over gold in terms of security. Guarding a lot of gold in a vault is expensive, but keeping a Brainwallet is not.

Really?
There is a reason why bank valuts have timed emergency locks.

Which brings up another hilarious Bitcoin Pascal's Mugging scenario: "What is the probability that you die, are cryopreserved, and are resurrected at some point in the future. But this future world is a dystopia, and cryoresurrected people are indentured servants of the company that revived them until they are able to pay back their debt. Since most jobs have been automated it is extremely difficult for you to get the money to ever earn your freedom. However, if you had created a Bitcoin brain wallet, you would be able to access it (because the cryoresurrection process is very good), and you would have something of value with which to pay off your debt and live comfortably in the new world".

They'll just extract the brainwallet from your memories using their advanced brain scan technology. Or a rubber hose.