Could the tagging system be enhanced to support tag synonyms?
Implement a Tag Black List
Some tags should be automatically replaced by other tags whenever a question is posted or retagged. This should be a manually maintained list of replacements that is applied automatically. Without that, all retag requests are pointless:
[as3]was retagged to
[actionscript-3], has again 552 new questions
[macosx]was retagged to
[osx], has again 513 new questions
[aws]was retagged to
[amazon-web-services], has again 37 new questions
[db]was retagged to
[database], has again 52 new questions
[rails]is constantly being retagged to
[ruby-on-rails], but has again 41 new questions
Just look through old retag requests for more examples.
If it is decided for a tag that mass-retagging it to another tag is ok, it should also be safe to extend this to new questions asked in the future. If somebody later tries to post a question with a "bad" tag, that tag should automatically be replaced with the "fixed" tag.