Re: 110.12
That would hard to enforce. Our shop wired a habitat for humanity house last year, 3 electricans, 3 technicians. One tech, is pretty sharp, you know the type with the pocket protector (really). He ran his NM at angles across the top of the ceiling joists. We said that was not allowed, he said its the "most logical" as it uses the least wire. But it would fail on workman like.
And this is a true story. This tech lived next door to Gary Larson of the Far Side fame in tacoma for 18 years. Many of the far side cartoons were based on this techs family and events, even down to the names.
Oh, and the Habiatat house was wired under a permit and inspection, we roped two in one very long day.