Pew Research Center: Tagging Play is a short report looking at who tags content on sites like Flickr, YouTube, Del.Icio.Us and the others.
I’d strongly recommend reading the brief report. There are some basic demographics in the report and short piece on what tagging means.
A December 2006 survey by the Pew Internet & American Life Project found that 28% of internet users — and 7% on any typical day — have tagged or categorized online content such as photos, news stories or blog posts.
(via Russ Weakley)