Existing Wording
Each resource may include a human-readable narrative that contains a summary of the resource, and may be used to represent the content of the resource to a human.
Resources SHOULD always contain narrative to support human-consumption as a fallback. However, in a strictly managed trading systems where all systems share a common data model and additional text is unnecessary or even a clinical safety risk, the narrative may be omitted. Implementers should consider carefully before doing this, as it will mean that these resources can only be understood in the limited trading environment. Closed trading partner environments are very likely to open up during the lifetime of the resources they define. In addition, many workflow steps involving finding and aggregating resources are much more difficult or tedious if the resources involved do not have their own text.

Comments
I suggest that resources SHALL contain a narrative (though there needs to be a way to express unknown data, as with CDA). The spec is ambivalent, saying first that a resource "may" include narrative, then later saying it SHOULD contain, and saying that no narrative is OK in a "closed trading partner environment." If the goal is interoperability as well as usability, why cater to closed environments? The standard should be optimized for the goals of openness and interoperability in the common case, not the edge case. After all, FHIR is premised upon NOT catering to edge cases (e.g., in its data model). Closed environments can use "closed" methods of exchange (such as custom messaging or custom services), or could create their own FHIR profile that defaults the narrative (if they really don't want it).

I also see that the Structure for the Narrative has cardinality of 1..1. Doesn't that mean it is required (which I agree with)? Is that inconsistent with the paragraph above that says narrative "may" or SHOULD) be included?

Grahame's Comments
we cannot get a requirement for all resources to have narrative to pass ballot; too many voters think that there's valid reasons to leave them out. Need to fix the root cardinality on the display- that's wrong and misleading. We don't create structures for edge cases, but we also don't make them illegal either.