You young, tech savvy librarians may not remember this article. But back in 1994 Nicholson Baker wrote an essay in The New Yorker titled "Discards." He argued that we were losing valuable data from our card catalogs as we pursued the "holy grail" of efficiency: the online catalog.
I thinks he was right. Well, now we have no excuse. It's not the card catalog this time. The local online catalog is now the dinosaur and we're being encouraged to pursue the next holy grail: the Web, that is, moving our integrated library systems (ILS) to the Cloud. Now we're being offered WorldCat Local.
This time there's no reason we need to lose valuable local cataloging data. We can merge our local records. As long as we put in the effort locally and there is a willingness from OCLC to do this. We will probably learn more from OCLC as time goes on. For now, check out the WorldCat Local FAQs [pdf].
So, before moving your ILS to the Web think about the added value that catalogers put into those local MARC records. You could be abandoning these records for the less-full master records in WorldCat. Think hard about this because if there's one thing we're learning about today's users: they want more information about resources, not less.