Academic Study on Tagging Systems.
I came across the paper "HT06, Tagging Paper, Taxonomy, Flickr, Academic Article, ToRead." Cameron Marlow, Mor Naaman, Danah Boyd, Marc Davis. Proceedings of Hypertext 2006. (pdf) The authors offer a model of web-based tagging systems, to help illustrate the possible benefits of these tools.
Exemplified in a study of Flickr's tagging system they analyze how (1) characteristics of system design and (2) user incentives and motivations may influence the resultant tags in a tagging system and show that the dynamics of interaction and participation are different than those of Del.icio.us. For example, since Del.icio.us is largely task-focused, namely storing bookmarks for future retrieval, organizational motivations are most dominant. Flickr users, on the other hand, are also likely to tag for their own retrieval, but coupled with an abundance of communication mechanisms, the system design encourages gaming and exploration of tag use. They show the consequences for usage and vocabulary formation.