"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"
L. Heller, R. The, and S. Bartling. Opening Science: The Evolving Guide on How the Internet is Changing Research, Collaboration and Scholarly Publishing, Springer, Heidelberg and New York, (2014)