Why not make this but for questions too?
I love that everything is well though behind SO but I can't see no reason as to why great questions can't be prized with "Badges by subject".
Tag badges are designed to emphasize knowledge in a particular field. For good questions, there are already the Good Question, Notable Question, Famous Question, Stellar Question, and Popular Question badges. However, since questions indicate lack of knowledge in a particular field, there is no good reason to create these badges.
Also, since people love to try and get badges, this would cause a great increase in questions because of people trying to get these tag question badges, which simply prevents people who legitimately need their question answered from getting an answer.