Social bookmarking sites like Delicious allow users to save, organize, and share bookmarks online. Delicious was launched in 2003 and was one of the earliest social bookmarking sites, allowing users to tag and retrieve bookmarks from any computer. It grew rapidly and was acquired by Yahoo in 2005. While social bookmarking provides advantages like collaboration and emergent vocabularies, it also presents disadvantages like informal tagging systems and potential for spam.