First of all I know Clay Shirky, and he's a good fellow. But he's simply wrong about his claim that "tagging" (of the flavor that is appearing on del.icio.us -- what I call "social tagging") is inherently better than the use of formal ontologies. Clay favors the tagging approach because it is bottom-up and emergent in nature, and he argues against ontologies because pre-specification cannot anticipate the future. But this is a simplistic view of both approaches. One could just as easily argue against tagging systems because they don't anticipate the future -- they are shortsighted, now-oriented systems that fail to capture the "big picture" or to optimally organize resources for the long-term. Their saving grace is that over time they do (hopefully) self-organize and prune out the chaff, but that depends both on the level of participation and the quality of that participation.