That's a clever setup that I hadn't seen before. Some extra downsides:
- Relying on emails for account recovery prevents creation of anonymous accounts.
- Have you ever lost your "convenience yubikey"? People underestimate how painful mass account recovery can be.
- The cost of 3 yubikeys can be substantial for some demographics.
- Important accounts are not properly backed up until you drive to your safe. That can be many days for a bank deposit box, or even longer if you're traveling.
Overall that's a lot of compromises for what should have been just "put this recovery key/password in a safe and forget about it until needed", if the protocol was better. And definitely not something that can be widely recommended.
- Relying on emails for account recovery prevents creation of anonymous accounts.
- Have you ever lost your "convenience yubikey"? People underestimate how painful mass account recovery can be.
- The cost of 3 yubikeys can be substantial for some demographics.
- Important accounts are not properly backed up until you drive to your safe. That can be many days for a bank deposit box, or even longer if you're traveling.
Overall that's a lot of compromises for what should have been just "put this recovery key/password in a safe and forget about it until needed", if the protocol was better. And definitely not something that can be widely recommended.