The phenomenon of folksonomy, the bottom-up categorization of content that lies at the heart of social bookmarking site del,icio.us and photo sharing site Flickr is catching on all across the web. Earlier this year, blog search giant Technorati began tracking user-generated tags and their tag page offers a constantly evolving topography of the categories of greatest current interest to participants. The ease-of-use and self-correcting nature of folksonomies underlie the success of the phenomenon, but inevitably debates arise. Today, Peter Merholz responds to an earlier article by Clay Shirky. Both authors see value in user-generated metadata, but Peter takes Clay to task for an ideological bias, claiming Shirky denigrates classic hierarchical organization schemes in favor of folksonomy. Peter argues for an integrated approach. Reading both articles goes a long way toward helping the rest of us make sense of this new and fascinating territory.