[Apple Developer Reference](http://developer.apple.com/library/ios/#documentation/Security/Reference/certifkeytrustservices/Reference/reference.html#//apple_ref/doc/uid/TP30000157)

> ***kSecTrustResultRecoverableTrustFailure***
> Trust denied; retry after changing settings. For example, if trust is denied because the certificate has expired, you can ask the user whether to trust the certificate anyway. If the user answers yes, then use the SecTrustSettingsSetTrustSettings function to set the user trust setting to kSecTrustResultProceed and call SecTrustEvaluate again. This value may be returned by the SecTrustEvaluate function but not stored as part of the user trust settings.

This is the reason expired or otherwise "questionably invalid" certificates are still allowed through the library. Removing this line means that we leave it up to the BOOL `self.shouldContinueWithInvalidCertificate` further down the script whether we continue on receiving this message.