Catalogers have always had to balance adherence to cataloging rules and authority files with creating cataloging that is current and relevant to users. That dilemma has been complicated in new ways because of user demands in the world of Web 2.0. Standardized cataloging is crucial for communication between computer systems, but patrons now have an expectation of social interaction on the Internet, as evidenced by the popularity of folksonomy. After a description of traditional subject cataloging and folksonomy, this article discusses several institutions where subject cataloging is still used, but where patron interaction is also encouraged. User-generated tags can coexist with controlled vocabulary such as subject headings.