Tagging is a hot topic for librarians

I have an uncomfortable feeling that a lot of old catalogers are rolling over in their graves. The idea of letting people choose their own tags! Can anarchy and chaos be far behind?
I have always been on the public service side of the library, so I am well acquainted with how people look for things. I have often served as an interpreter, as in, "Let's try this subject heading--or that subject heading."
When our automation system came online, we were so concerned about the subject headings that we placed copies of Sears List of Subject Headings at all OPAC locations. If you are too young, or not into cataloging, this is an 80-year-old resource and guide and was, at the time, a large red book that weighed about 30 lbs. Did anyone EVER look into that book? No. Did they use keyword search? You bet! It wasn't long, in fact, until all of us librarians were using keyword search most of the time.
I have come to the conclusion that it would be added value if people put their own tags on our collection, in addition to the proper librarian-assigned subject headings. People will look for things the way they want to look, and arrange things to their liking, and feel more ownership if we allow them to have some input. The language and our knowledge base are evolving rapidly, and I don't think we can keep pace with it using the old traditional processes.