Material Types in Library Science and OLAC Types

One of the frequent things I hear about OLAC is a critique of its Resource Type vocabulary. The OLAC application profile adds linguistics resource types in addition to DCMITypes and an unqualified DC type value. What I don't hear from these same cries for additional descriptive power is for a structured way to use any of the existing resource type vocabularies. Let me list a few:

It has been argued that the Dublin Core Type field is an example of a genre field. This may be true in some sense, but I have a tendency to think of it in terms of an interactivity type field; more of a modality field.