Tools such as blogs and wikis allow users to upload and share information online. Sites such as YouTube and Flickr permit people to load and share content. Social networks including Facebook and LinkedIn encourage online interaction, and can be used as a forum from which to extract the so-called wisdom of crowds or to perform sentiment mining.
In a library setting, web 2.0 tools allow users to collaborate with one another and librarians in terms of indexing or authenticating information, use tagging to identify valuable information collections, or develop metadata describing those collections.
This will make the librarian-user relationship more dynamic, and also encourage more user-generated content to be shared and potentially reused in mash-ups under a creative commons licence.