After reading many threads here, I think the final ruling may be: - If your record represents a physical being or object: Use a surrogate key. People change.

After reading many threads here, I think the final ruling may be: - If your record represents a physical being or object: Use a surrogate key. People change. Unrelated - if you have a list of emails or SSNs or license plates or VINs - we can think of these as foreign keys to a database we don't control.