OCLC has published a report called, Implications of MARC Tag Usage on Library Metadata Practices[pdf]
I've only begun to read it.
The "implications" section of the Exec. Summ. are interesting.
1. Be consistent. Splitting content across multiple fields will negatively affect indexing, retrieval, and mapping to other encoding schema.
2. Respond to local user needs whether that is counting plates in a book or adding contents notes.
3. Focus on authorized names, classifications, and controlled vocabularies that key word searching of full-text will not provide (as full text online negates some value of descriptive surrogates).
4. Use specific MARC fields for particular types of note if they are available rather than the general 500 note.
5. Map the 200 or so MARC 21 fields in use to simpler schema. (MARC data cannot continue to exist in its own discrete environment, separate from the rest of the information universe. Leverage it and use it in other domains to reach users in heir own networked environments.)
6. Accuracy of fields that are used in machine matching becomes more important in environments using linked data to leverage fuller descriptions and other related information generated from other sources.
And MARC's future:
1. MARC is a niche data communication format approaching the end of its life cycle.
2. Encoding schema will need to robust MARC crosswalks to ingest millions of legacy records.
3. How would we create, capture, structure, store, search, retrieve, and display objects and metadata if we didn’t have to use MARC and if we weren’t limited by current library systems?
4. How do we best take advantage of linked data and avoid creating the same redundant metadata in individual records?
5. How do we integrate library metadata with sources outside the traditional library environment?
6. To meet the demands of the rest of the information universe, give priority to interoperability with other encoding schema and systems.