As a new member of this mailing list, allow me to introduce myself and the institution I represent.
I am what we call in our jargon the Semantic Web Activity Lead at the W3C. What this means in practice is that I initiate and coordinate most (if not all) Semantic Web related groups at the W3C and I am also responsible for the outreach activities around the Semantic Web.
I was very excited to see the initiative of the US Library of Congress. From my point of view, this initiative will be an important contribution to the vision of the Semantic Web or, to use another term, a Web of Data on which library data at large would at last take its well deserved place.
I will not repeat that arguments on the benefits for the Library Community of using Linked Library Data. This has been documented in a report of a W3C Incubator Group; they have made a much better job that I would ever do. However, I can express why I believe such a synergy would also be beneficial for the Semantic Web community. Indeed, the Semantic Web envisions a Web of Data, i.e., a place where different types of data can be integrated, used by applications or by end users, regardless of the origin and the exact location of that data. The Web has given us this for documents; it is time to have the same for data in general. However, it is inconceivable to envisage this without the huge amount of data, repositories, catalogues, accumulated knowledge, etc, that is available in libraries around the globe. Furthermore, and that may be less obvious to the library community, the unique experience that this community has in cataloguing, archiving, and managing resources can bring a hugely important extra experience and knowledge to the Semantic Web community, research and development alike.
I am not a librarian. This means that there are many technical and social issues discussed on this list that I cannot really contribute to. However, I would be very pleased to provide feedback, whenever that is necessary, on specific, Semantic Web related technical questions concerning the intricacies of RDF, OWL, SKOS, or SPARQL. I would also be happy to take the problems raised by this group and feed them back to the relevant Working Groups that are currently active at the W3C (see, for example,  for some of those). I.e., I hope I can be of help.
Of course, there may specific technical issues and solutions coming up in future that might require further standardization in future; W3C may have a role to play then and I will be happy to discuss this if and when the time comes.
Ivan Herman, W3C Semantic Web Activity Lead