Uber Tag Search?

Brian Dear imagines a search engine where all user-generated tag information is searchable – an engine that confederates the various nations of Flickr, iTunes, etc. Neat idea, and certainly another step toward the semantic web vision.

. . . if more and more services in 2005 add user-generated tagging, will “federated tagging” be far behind? And if someone were to index all the tags from these various sites…. would the result be Taggle? Imagine: a service where you type in a keyword, and you get back all the hits that have that word as a tag. If Flickr, del.icio.us, and umpteen other sites cooperated, then an uber-tag-search service might just work . . .