Tags do not fit spatial memory. Tags are utterly worthless in any spatial context. You're at the mercy of a search engine's implementation and index foibles fo

Tags do not fit spatial memory. Tags are utterly worthless in any spatial context. You're at the mercy of a search engine's implementation and index foibles for finding things through search queries. A hierarchy maps onto our spatial memory, which we use to figure out where we've been and go back to it. There's a lot to be said for maintaining spatial metaphors in information space. Another little detail here is that spatial organisation (in meatspace) is a shared environment. A single 'shared' ontology is useful even if it's nonsense, because it's still a shared frame of reference in which navigational directions can be shared.