Has anyone ever thought about having tags for answers in addition to the tags for questions? That is to say that when someone writes an answer they would be able to assign tags to the answer separate from the tags on the question. My feeling is that this could be useful because oftentimes answers branch off from the question and touch upon other areas that wouldn't be covered by the tags in the question. If someone is looking for something based on tags, the tags in the question don't necessarily adequately represent the content in the answers.
This is probably a general StackExchange question, but I think that it might be particularly useful for Mi Yodeya.
What would be the pros and cons of such a system?
Is it feasible in any form?
Am I the only one who thinks it would be beneficial?
(I did find this discussed here, but the discussion there seems to be about classifying the answers as relating to the questions, whereas I am discussing a system for categorizing answers irrespective of the questions.)