It would be cool to be able to tag tag entities.

It sounds like a joke, but it really would be nice to be able to browse via interlinked tags. We already have genre relationships (which rules) but it would be cool to (just as an example) click on the 'video game music' tag, and see that the top user-added tag is 'the elder scrolls', and then see tags for 'morrowind', 'skyrim', 'beyond skyrim' etc on that tag as well.

The main uses (that I can imagine) is for:

• People browsing MusicBrainz casually, looking for stuff, where this could provide a crazy-cool exploration of user-added branching paths
• Editors who are adding tags - for instance, sometimes there's different possible ways of entering a tag, or you're not sure what tag to use, and it would be useful to be able to see existing tags that have (for instance) 'the elder scrolls', maybe before adding new tags for 'elder scrolls'