Imagine that you are very popular in a Forum XYZ. And you've just seen a movie that you didn't like and you want to create a forum topic cursing about that movie. But you do not want that other users see your posts identity. But if anonymizer module is enabled and the proper permissions are configured correctly, you may check a button which says "Post anonymously". And you will see that your post is anonymous. And people will not see your username in the forum topic. Thanks anonymizer module for this terrific trick ;).
This is awesome but anonymizer module is currently working for drupal 6.
An upgrade should be done so that it also works in drupal 7.
Let's rock doing a new version. Yeah !!!

The new module for drupal 7 will have the same as version 2 but with some upgrades like:
-Usability
-Documentation

The permissions will be:
-Administer
-Post anonymous nodes
-View hidden author

Cases
If permission "post anonymous nodes" is actived.
A user logs in, creates a node, clicks in Post anonymously.
The same user watchs his post and just see
Fri, 2012-06-01 15:18 — Anonymous
Author: username

If the permission of "view hidden author" is actived.
Any user may see the post but now with the following format:
Fri, 2012-06-01 15:18 — Anonymous
Author: username

If the user does not have permissions just see
title
body

Check anonymizer module sandbox project here