This post is part of the Radical Reference Library of Congress Subject Heading Suggestion Blog-a-Thon.

FOLKSONOMY was first proposed to the Cataloging Policy & Support Office in September 2007 by Sanford Berman.

I refer you to items in your own catalog for documentation.
Blogs, Wikipedia, Second life, and Beyond : from production to produsage by Axel Bruns, held by the Library of Congress, which has a chapter called "Folksonomies : produsage and/of knowledge structures." and Library 2.0 and beyond : innovative technologies and tomorrow's userby Nancy Courtney, which has a chapter called "Folksonomies and user-based tagging," by Ellyssa Kroski.

Further warrant can be found in Daniel's H. Pink's having published an article in The New York Times about it, Folksonomy from December 11, 2005.

It might also be of interest to note that a Google search on <folksonomy | folksonomies> returns 2,000,000 results. (However, please do not take my suggestion of adding FOLKSONOMY as a subject heading to be a recommendation to replace subject headings with it altogether. As an academic librarian working with researchers every day, I still heart controlled vocabulary, not to mention skilled, experienced catalogers and the work they do. See "On the Record" but Off the Track: A Review of the Report of The Library of Congress Working Group on The Future of Bibliographic Control, With a Further Examination of Library of Congress Cataloging Tendencies by Thomas Mann.)

Note that I have delicious tagged (folksonomized?) this post rr_lcsh2008 and for:radical_reference