In a msg to gcs-pcs, Tony Hammond, who one of the authors working on social bookmarking, writes:
These papers describe the current state of play with respect to the new crop of web-based bookmark managers - tools such as del.icio.us and Flickr are well-known exemplars of the genre. These papers describe how such tools can be specialized as web-based reference managers.... Bookmarked references can be shared with other users and can be publicly commented upon. In fact, whole discussion threads can be built up around individual bookmarked references. (The papers are set up as living examples with their own reference lists available online both for comment and further additions.) Import/export opportunities within Connotea include RSS and RIS - support for other formats is under development.
I love the idea that del.icio.us and Flickr are "well-known exemplars."