Logging has its place, but I'd argue it's far more important that great programmers write code that fails fast. In his example, he didn't have instrumentation in production to determine why a module was returning null. If null isn't an expected return value, then an exception should be thrown to avoid the system moving forward in a crippled and unpredictable state. A well tested system that stops processing and fails fast with a descriptive exception greatly reduces the need for time-consuming and resource depleting logging systems.