Fingerprints are also one of the most promiscuous of biometric indicators possible. You leave your fingerprints just about everywhere you go, which can be picked up with some powder and sticky tape.

I would never consider my fingerprint to be a secure form of identification, nor should systems be designed that make this assumption.

I don't know I can see fingerprints being more secure than 4 digit pin. I can watch people enter their 4 digit pin and memorize just by standing next to them on the subway. I can't do the same thing with a fingerprint.

It's possible you could actually lift a usable fingerprint off the surface of a phone that you find. We leave them everywhere.

That's a good point. But while it's permanent it's at least harder to replicate for the time being.