Identity failure / Corruption – Root cause

For the third time in a year and a half I was unable to open Outlook getting a message that my identity needed to be rebuilt.

The rebuild failed and I had to piece together various methods gleaned from these forums and elsewhere on the net to get a semblance of recovery.

My question is: What causes this Identity corruption? What can I do to avoid it?

I have seen many work arounds to fix but nothing to indicate a cause.

Thanks

Question about Outlook Express