bbPress.org

I think that site naviation really depends on how much traffic your forum has, how much you want it to have, and in what route you want your traffic to reach its destination.

The typical forum layout comes from catering to new visitors that want descriptions of each category, and from repeat visitors wanting to check if there are updates to that category without having to click into that category.

Tags don’t offer either of these options inherently.

If tags could visually signify if there are new posts for the visitor inside of them, maybe with emphasis or italics or reordering them to the front of the cloud, that would be a neat idea.

bbPress tends to take a different approach on forum/topic importance, by emphasising on the most recently replied to topics right on the front page. I consider this more of a feature of a slow moving bulletin board more than for a large one. I know some large technical forums that would show 20 different posts on every page refresh with this type of last reply based concept.

Tags are interesting because they are user editable and provide a wiki-esque style of topic organization. 99% of users will obey this, but it still requires a bit of moderation and attention. Using categories that users cannot edit allows for you to legitimately categorize your data, rather than have it free flowing any and everywhere. Also, how do you compensate for the “New Topic” screen where there is a category drop-down? If your authors aren’t familiar with the concept and meaning of your forums categories, yet they are forced to choose one, this will result in topics being put into the database almost at random, making it difficult for you to moderate them.

I see how this idea can be appealing, and I see how it could work in some instances, but I think this type of idea is more suitable for a WordPress type blog/CMS than for a forum.