edutagger is a social bookmarking service for K-12 learners and educators, allowing you to store your web links online and share them with others, all within an educational context.
Diigo is about "Social Annotation", a superset of social bookmarking. We believe that the social annotation service provided by Diigo can really enhance your experience for online browsing and interactions, and for information gathering and sharing.
Shirky begründet, warum es z.B. beim social bookmarking sinnvoll ist, a posteriori einfache Begriffe als Tags zu verwenden - statt zu versuchen, eine übergreifende hierarchische Organisation der links zu schaffen.