Currently, tags on wiki pages as implemented by TagsPlugin are either present or not, with no record of who added the tag, when it was added, or if it was removed. Since the tagging table only contains a
(tagspace,name,tag) tuple, there doesn't seem to be room in the current implementation for even storing the "author" of a tag on a certain wiki page, its history, or its destruction.
This seems contrary to the wikinature of the rest of trac, and certainly leaves the tickets (with their automatically revision-tracked keywords) looking much healthier. I'm not sure how one would make the transition for existing systems, but could the TagsPlugin be moved to a more wiki-ish model?