I bet you will like findability guru Peter Morville’s article on Authority [in the librarian sense] even more than you might otherwise because of its beautiful design and high readability.
You see, tags are only the visible, superficial symbols of a much deeper, more interesting revolution in findability and authority. Wikipedia doesn’t beat Britannica because it has better folksonomies. It wins because it’s more findable. And its success didn’t come without structure. In fact, the Wikipedia has a traditional information architecture (with strong design conventions and a fixed left-hand navigation bar) and a traditional governance model (with Jimbo Wales and his Board of Trustees as the ultimate corporate authority).