This social bookmarking tool has structured tagging. Seems like a move towards what cataloging librarians have been doing for years: creating subject headings.
Description from their homepage:
"Faviki is a social bookmarking tool which allows you to tag webpages you want to remember with Wikipedia terms. This means that everybody uses the same names for tags from the world's largest collection of knowledge.
Thanks to DBpedia, which extracts structured information from Wikipedia and represents it in a flexible data model, these tags are reference to objects which are categorized automatically, keeping your and your friend's bookmarks and interests well organized."