This came up recently in some AUTOCAT posts, in a discussion about retaining or deleting relator terms and/or codes in records. Back when our Validate Headings Wizard was much more sensitive, I used to delete all relator codes and terms, because they made it impossible to properly validate name headings that had them. Now, I retain them - who knows, we might one day actually be able to make use of them in the way that WorldCat Identities does.
Of course, even WorldCat Identities can give out garbled results when it only has garbled data to work with, as can be seen in that example from AUTOCAT. John Adams, an active writer from 1651 to 2008, is rarely written about although he himself is a prolific writer of such varied works as erotic fiction and children's stories. He is a businessman, mayor, and legislator, as well as a performer, conductor, speaker, and more. Truly, this is a renaissance man. Or maybe vampire.