Tags work well for blogs, but I don't think they are a good idea for a message board, especially one the size of this.
That's why I abandoned the plans for the tag system.
In addition to my reply above about everyone assigning any topic to any section, it could be a good idea to simply limit the creation of new virtual sections on demand.
So if a few people decide they want to "establish" a new virtual section, we would create one and they would be in charge of assigning topics to it.
Maybe that would work.