Steve Rubel writes:
"Tags are free-form keywords people have used to describe their posts [...] and are a natural complement to search because they empower users to create structures that organize unstructured consumer-generated media.
As tagging takes off, the next step will be for all of these sites to monetize this content by launching contextual advertising programs, perhaps powered by Google Adsense. This will give the marketer new ways to reach engaged consumers by sponsoring tags across one or more sites that carry folksonomies. I call this "Tagtextual Advertising" and it's a coming."