biometrics are not "better"
"Iris scans, electronic fingerprinting and signature recognition – they're certainly better than jotting a password down on a post-it note."
No, they're not. Biometrics are not "certainly better" than recording a password somewhere - even though passwords are a miserable authentication mechanism.
Biometrics have a number of nasty failure modes; I'd much rather have someone steal a post-it from me than a finger. Simple biometric systems make secret-sharing and key escrow difficult. And so on.
A strong password performs as well under almost the same threat model as a biometric system. Biometrics are stronger against some attacks (eg some social-engineering attacks) and failures (eg forgetting a password that's not recorded somewhere), but those can be mitigated in a password system.
And recording a password on a post-it may not be a significant vulnerability under a reasonable threat model. I keep a paper list of my passwords in my office. Since my office is in my home, and the list is in my safe, it's doubtful any attacker would use that vector. Easier just to compel me to reveal passwords by force.
In security, few simple statements are "certainly" true. Security is complicated and highly sensitive to context.