I would say no. Teaching students how to use the card catalog, whether physical or electronic, is useful. But the Dewey and Library of Congress Systems are nothing more than ways to number the shelves, really. Having students memorize the system is rather pointless; I don't need to know how Google organizes its information internally to get what I want online, after all. The crux of the matter is: Can you find what you are looking for? As long as a student can use the catalog and read the tags on the shelves, then they are set on the cataloging issue.
Of much greater import is the point that #7 makes; what most students really need to learn is how to search effectively. This includes understanding how to make a list of key words or tags, and a grasp of the different types and qualities of references that are available to them. All you have to do is look at how poor a job most students do at putting tags on their enotes questions to realize that knowing the Dewey decimal system isn't going to help them find information - organizing their thoughts so they know what they are trying to find has to come first.