I strongly believe that an anonymous posting feature is a great way to evolve from the usual forum systems - as evidenced by popular boards such as 4chan.
I’m not sure if the developers are too keen on making such a feature but I’m willing to pay for a plugin.
So the specifics are:
- allow a registered user to make posts anonymously via a checkbox
- allow unregistered users to post as anonymous
- allow an option that makes a category anonymous only (wherein all posts within that category will be anonymous, regardless if the user selects the anonymous checkbox or not)