Accumulating and intersecting categories

As this blog evolves, I'm interested by the process of tagging its posts into categories and observing where they fit.  In essence, the tags reflect a taxonomy of interests, updated incrementally.  It struck me that the preceding post was the first one that qualified for three preexisting tags, demonstrating appeal (at least to me) in several distinct dimensions. I often think that the most intriguing topics to consider are those that are hard to characterize, or that could fall equally well into several alternatives.  This can be a problem in bookstores, where a finite number of physical copies must be placed into one (or sometimes a few) shelves with fixed themes, but can be easier to manage when it's possible to create and manage multiple tags.  Nonetheless, it's only effective if tags are selected usefully: too few, and they're not helpful; too many, and the tag space itself becomes hard to grasp.