It's a fairly common occurrence for newer users to the SE network to post a question with very specific tags to a question, but not a more general, larger tag that is also appropriate. For example, this question on Stack Overflow should be tagged Java, but isn't. If that question were a duplicate, a Java gold badge holder would not be able to close it as a duplicate. (Of course, BalusC has a gold badge in jsf as well, but that's besides the point).
I think that we should also give dupehammer privileges to users that:
- For very small tags, have a bronze tag badge in that tag
- For medium sized tags, have a silver tag badge in that tag
- The user has a gold tag badge in a tag that is on the top three tags in the Related Tags list.
For example, in the question I linked above, if you had a silver badge in jsf, and a gold badge in Java (because it's the #2 Related tag), you would be able to dupehammer this question. In the case of jsf, this would give 5 additional users dupehammer privileges.
Update: both answers make a great point that this wouldn't really work on Meta sites because the tags are pretty skewed (mandatory tags etc.), this change should be for main sites only.
I didn't add this as an answer to this because it's not a power granted to all silver tag badge holders, you need to have two badges.