"someone edited a zone file, and put an invalid character in it, and reloaded bind. Bind gave a syntax error but kept using the old zone file."
I use multiple Icinga checks for key DNS records - use a monitoring system for monitoring. I keep a list of "bootstrap" IP addresses stored in two places and a time-stamped print out - that's part of our BC and DR plan.
You do your risk assessments (often based on bitter personal experience) and then you mitigate the risks. One person's memory is not a valid mitigation for most organisations.
I do have a few IP addresses committed to memory but only by accident.