Here's a site I run. As you can see, the forums have been categorized into "Friendly Talkzone", which contains everything, and "Politics and the war", which contains political posts. I created the second forum so that people not interested in this topic could ignore it by only reading the other forums.
Now, there is demand for a "Relationships & Fiancee visas" forum, again, so that people not interested in this topic can easily ignore it.
I am thinking about the consequences of categorization. Creating a category legitimizes the category. It means there will always be a place on my site for those discussions, even when nobody wants to have them anymore. And I have the feeling there are other social effects of creating a category like this.
(PS: The Friendly Talkzone is the "Everything Else" category.)
Thoughts on the social impact of categories on online discussions are very welcome!