The principle of accountability has been described in many references; it is a principle by which specific action can be traced back to an individual. As mentioned by Idrach, any significant action should be traceable to a specific user. The definition of "Significant" is entirely dependant on your business circumstances and risk management model. It was also mentioned by Rino that tracing the actions of a specific user is fine but we must also be able to ascertain that this specific user was responsible for the uninitiated action.

"Kerberos is an authentication protocol and was designed in the mid-1980s as part of MIT's Project Athena." Pg 129 Shon Harris: All-in-One CISSP Certification

Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide:
Mastering the Ten Domains of Computer Security, page 222.
"System crash" and "system failure" are the key words. One "recovers" from a crash or failure.