After reading the Wikipedia article on tagging (http://en.wikipedia.org/wiki/Tag_(metadata) ), I understand the concepts involved more clearly, although I understood the basics.
I first understood the utility of tagging on the Flickr project. For instance, a picture of a red rose against a red background of another shade might be important to some because the picture is a rose; the red background would be of little importance. For others, the important concept would be the illustration of the color red using a red rose on a red background. Both the tag “red” and the tag “rose” could operate as the most important term, depending on the searcher.
I think tagging is a useful addition to standard subject headings in a library environment. They can be very useful.
Web2Access does evaluate the tagging feature on some sites (http://www.web2access.org.uk/activity/9/) but not on my blog site, WordPress. The activity on Web2Access is called “Keywords Labeling Data.” That may change, and I will post an update.
Web2Access rated Wikipedia (http://www.web2access.org.uk/product/6) as fairly accessible, overall, saying that “On the whole these web pages tend to be screen reader accessible and navigable with a keyboard. The registration may need an e-mail to the administrator.” The score for those with blindness/visual impairments was 73%, and for partial visual acuity and visual stress, 78%. They were lowered because any user may add content, without oversight as to whether or not the content was accessible.