Once again, let me play my broken record---there is demonstrated by many professional librarians a sad lack of understanding of the purpose of knowledge classification systems--how to build/construct numbers for representing the intellectual content of a resource in order to show how that content is related to other resources in the collection (i.e., fits into the collection). How would the user know how to read the numbers if the librarian doesn't even understand it?
DDC, LCC, etc., are knowledge classification systems first, not physical arrangement devices. Physical arrangement is a by-product; using the class #s for shelf-arrangement is optional. I only hope these libraries that have switched to something like BISAC (sp?) haven't stripped the DDC numbers completely from the record.
As a former dilettante-theorist of the history of classification, one thing I took away from my studies is that any classification is only a mirror of the mind of the person who made the classification. What I mean by this can be seen just by perusing the outlines of any classification scheme: with some consideration, you can know if the classifier believes in God or not, what they think about moral or political questions, when the classification was created, and so on. Sometimes, it is absolutely obvious, such as some medieval classifications that began and ended with God ("I am the alpha and the omega") or in our own LCC, which classes Communism after criminal organizations such as the Mafia. Also in LCC, we see the importance they placed on philosophy in the 19th century, e.g. an entire subclass BH devoted to Aesthetics. The user of the classification system is also locked in time, e.g. Psychology, which is seen as more of a science now and would probably be more useful for browsing purposes in R, is still in B. Examples can go on and on, especially when comparing different systems. That's why I am not surprised that the Open Shelves Classification hasn't been much of a success. Too many cooks spoil the broth.
It wasn't until later when some of the bigger book collections began to be built that what we know as library classifications came out. Of course, the librarians almost always placed related books together, but a classification number normally referred more to an alcove with a big letter over it: "Z" which stood for e.g. Religion where you would go and browse the limited number of shelves of books, where everything got a shelf or press number. Here are some examples at Princeton: http://infoshare1.princeton.edu/rbsc2/libraryhistory/shlfmks/shelfmarks.html
I have gone back and forth about the utility of retaining the classification *number* in an online environment and I have argued strenuously against them in the past, but I think I have changed (for the moment!) and see their use more as a handy ordering device behind the scenes for the associated text that describes the subject (the label). For example, "Abnaki Indians" with E99.A13, the number would be used primarily for arranging the different headings for browsing, which gets away from alphabetical arrangement or the handmade BT/RT/NT, and the number may not even have to display.
But I don't know.