Yep, Library 2.0 continues to be a hot topic in the world of library and information studies. Is it really all that different from Web 2.0? No, I don't think so. It's just the application of social networking to the library world.
Some librarians are gung-ho for Library 2.0 applications like using blogs to keep users up to date, but others are reaching for the AACR2 to try and keep a controlled vocabulary in 'control' of the catalog instead of the user-defined tags that are popping up everywhere.
Applying social networking to the library environment is a great idea, but we still have yet to reach the point where a critical mass of users have adopted the tools and jumped into following library RSS feeds, blogs, and tagging in the catalog.
There are plenty of great things about applying Web 2.0 to the library, but let's be patient as the rules of engagement evolve...