• Tagwebs, Flickr, and the Human Brain (by Jakob Lodwick)
  What if we could tag not just photos, but also other tags? We could start to build a tagweb. When a tagweb is created from your tags, that tagweb works perfectly within the realm of what makes sense to you. The reason nobody came up with this before Flickr was because we didn`t have Flickr as a visible reference point. You can`t just imagine something out of the blue without first thinking about related things.
  in Public bookmarks with folksonomy ontology semantic tag tagging

tagging from all users