At least in crypto, that's why things like the Ledger or Trezor are really important, at least if you're storing any non-de-minimus amount. Protects against things like 0-days, etc.
How would Libra ever work if general population using it have the normal level of computer security?
I foresee a headline like: "$20m worth of Libra stolen due to newly found security flaw. Facebook says 'sucks to be you, it's irreversible'".
(or is the protocol different, and it is reversible? How? Who controls that?)