Any kid who's successfully forged their parent's signature on school forms has demonstrated the flaws with biometrics as single-factor auth.
@kyle Sure, but it's worth noting what we're comparing it to. It's possible to spoof a biometric, but it's also possible to shoulder-surf someone's passcode. When in public, I'd honestly consider that a greater risk than someone printing a replica fingerprint to unlock my device.
Different auth mechanisms have tradeoffs for different threat models, and I think that's fine so long as you're aware of them. When crossing a border? Sure, I'll disable biometric auth.
@jfred I'd consider using biometrics as a *second* factor along with a long PIN, but unfortunately at least on Android the assumption is one or the other, not both.