On Library 2.0 & Web 2.0

My thoughts about library 2.0 & web 2.0...The "just in case" collections rang a big bell with me. I am taking a managing collections class this spring semester. I am hoping to learn some new ideas about managing collections. Do we keep those "just in case" collections? Do we get rid of them just because there's an on-line version available and people haven't asked for those old tomes in the deep recesses of our libraries? Where do we draw the line on what we keep and what we don't? I hope to learn different philosophies on these questions and formulate my own opinions. I think it would be really neat to be able to use tags (user centered, not Dewey centered) in a card catalog. I know some libraries do. Tagging is a concept that's familiar to our users. It would eliminate trying to outguess Dewey's subject headings (which, for those of us who haven't worked in libraries for years and years, is problematic when trying to answer reference questions). I think we need to meet our users in interfaces that are comfortable to them, but not get so trendy that we forget our most important rule (in my opinion)...customer service.