In a long article about insecurities in gun safes, there’s this great paragraph:
Unfortunately, manufacturers and consumers are deceived and misled into a false sense of security by electronic credentials, codes, and biometrics. We have seen this often, even with high security locks. Our rule: electrons do not open doors; mechanical components do. If you can compromise the mechanisms then all the credentials, encryption, fingerprint readers, and other gizmos and gimmicks mean nothing.
In other words, security is only as strong as the weakest link.
EDITED TO ADD (8/13): DefCon 19 talk on the security of gun safes.