I less than one year, StackOverflow has **accumulated 23,305 tags** (as of this post).

Should higher-end moderators have an interface to **rename, combine, and delete tags** at the database level (i.e. beyond editing individual messages)? 

Most changes would be fairly obvious:

 - **Formatting inconsistencies** like "`visualstudio`", "`visual-studio`", "`visual+studio`" could be combined.
 - **Word Variations**: `reference`, `referencing`, `references`
 - **Obvious user error**: the tag "`best practices`" becomes two  - "`best`" and "`practices`"
 - **Obsolete or tags made irrelevant**: `visualstudio2010beta1`

There will always be the fringe cases and judgment calls. If a proposed change is that controversial, it could be discussed here (meta.SO), where appropriate. 

Maintaining a completely sanitized tag cloud is difficult to impossible. I'm not even suggesting that. But there might be a place for a bit of routine maintenance and sanity checking. This is best done on an on-going basis rather than all at once.