The OCLC folks are all abuzz with the addition today of the billionth holding to Worldcat, as reported all over. This is obviously an enormous milestone for OCLC and for libraries in general. Kudos are in order for all of us, I think!
The union catalog has transformed the way libraries provide access to their material. A billion holdings in one database seems to me to be proof positive of that. But OCLC Research staff and many others, researchers and practicioners, aren't content with the functionality our current union catalogs offer. The enormous wealth of data represented by those one billion holdings has the potential to be used in innumerable ways. I believe OCLC's FRBR activities are excellent examples of the sorts of creative things we can do with this data to better serve our users. We've made huge strides in access to materials, yet we have many miles to go.
UPDATE: I've discovered today the misfortune of having a book on The Monkees be Worldcat's one billionth holding. We're going to have a country of librarians walking around for two weeks now with that damn theme song stuck in our heads!