The purpose of the Tag Wiki is two-fold:

 - So Users will know what a Tag is for
 - So Users will know how to use a Tag

A Tag Wiki **is** Meta information.  We should not try to sanitize them to just be wikis about the subject, they are wikis about the Tag which is a Meta object in and of itself.

Here's the official [blog post][1] on the subject, a relevant portion is:

> Here’s a few words of advice on
> writing tag wiki excerpts:
> 
>  1. The excerpt is the elevator pitch for the tag
>  2. Avoid generically defining the concept behind a tag, unless it is
> highly specialized. 
>  3. Concentrate on what a tag means to your community.
>  4. Provide basic guidance on when to use the tag.


  [1]: http://blog.stackoverflow.com/2011/03/redesigned-tags-page/