From their site: del.icio.us is a social bookmarking website -- the primary use of del.icio.us is to store your bookmarks online, which allows you to access the same bookmarks from any computer and add bookmarks from anywhere, too. On del.icio.us, you can use tags to organize and remember your bookmarks, which is a much more flexible system than folders.
The API provides read/write access to Delicious bookmarks and tags via an HTTP-based interface. The RESTful API returns responses in XML.
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So far, we don't have a record of any changes to this API