After an excellent talk today about LibraryThing by LibraryThing's Tim, I got enthused to see how LibraryThing stacks up against other libraries for having matches in it's authority control system for entities we (the NZETC) care about.
The answer is averagely.
For copies of printed books less than a hundred years old (or reprinted in the last hundred years), and their authors, LibraryThing seems to do every well. These are the books likely to be in active circulation in personal libraries, so it stands to reason that these would be well covered.
I tried half a dozen books from our Nineteenth-Century Novels Collection, and most were missing, Erewhon, of course, was well represented. LibraryThing doesn't have the "Treaty of Waitangi" (a set of manuscripts) but it does have "Facsimiles of the Treaty of Waitangi." It's not clear to me whether these would be merged under their cataloguing rules.
Coverage of non-core bibliographic entities was lacking. Places get a little odd. Sydney is "http://www.librarything.com/place/Sydney,%20New%20South%20Wales,%20Australia" but Wellington is "http://www.librarything.com/place/Wellington" and Anzac Cove appears to be is missing altogether. This doesn't seem like a sane authority control system for places, as far as I can see. People who are the subjects rather than the authors of books didn't come out so well. I couldn't find Abel Janszoon Tasman, Pōtatau Te Wherowhero or Charles Frederick Goldie, all of which are near and dear to our hearts.
Here is the spreadsheet of how different web-enabled systems map entities we care about.
Correction: It seems that the correct URL for Wellington is http://www.librarything.com/place/Wellington,%20New%20Zealand which brings sanity back.