"tagging eliminates the decision - (choosing the right category), and takes away the analysis-paralysis stage (...) it provides immediate self and social feedback (...) it taps into an existing cognitive process without adding add much cognitive cost"
"Tagging works because it strikes a balance between the individual and social. It serves the individual motive of remembering, and forms a ad-hoc social groups around it."
"Could the order of tags be a general solution for hierarchical tagging? It would be similar to relations between words within sentences or to the order of folders in a directory and without enforcing a structure."
L. Nelson, C. Held, P. Pirolli, L. Hong, D. Schiano, und E. Chi. CHI '09: Proceedings of the 27th international conference on Human factors in computing systems, Seite 1795--1798. New York, NY, USA, ACM, (2009)