Stowe Boyd makes a good point about the key adoption hurdle for open tagging:

However, the assertion that we can start merrily open tagging (tra la) with XRIs fails one critical test: I would like to have taggregators like Technorati accept these tags as equivalent to the closed URL-based tags currently in use. Without that major shift in the tag ecology, XRIs have a long road before migrating into general use.

I couldn’t agree more – XRI can solve the technical part of the open tagging challenge, but not the social part. I would offer this thought: given that almost by definition any Open Tagging standard (de facto or official) must not require a single central dictionary authority, it presents the classic open systems challenge: which of the current taggregators is going to migrate to a truly open dictionary until they are forced to? And if so, what would that forcing function be?

Until that question is answered, Stowe’s right — we won’t have open tagging.