UTB would be the FYAD of this forum. And forums like that are always, always hidden from non-registered users (unless you get an account , you don't get to see forums like FYAD, Something Awful doesn't want new users to even know it exists).
Essentially, sections like UTB always serve as the absolute last stop for what's allowed on the site. Trolling that goes too far even for JBO, but still allowed here (just hidden away). Anything more extreme wouldn't be allowable on any forum anywhere anyway.
The biggest plus to having this type of subforum is that it keeps the lighter areas clean and free from those kinds of posts. When the most vile posters have their own hangout, they tend to leave the tamer areas alone and cause less trouble for the mods and admins. Also, it's easier to keep them in check when they all congregate in one area.
But ultimately, this depends on the admins' stance on JBO: is JBO the furthest they're willing to go with content on this site, or do they feel like there's a higher level of fukkery that they're willing to allow here? They might respond to this by hiding JBO even more and making the rules even more LAX, but some JBO posters might not want that.
Even if the forum is hidden, we don't know what they're comfortable with here. You might have to go another site if you want to post things that are too much even for JBO. Either we'd already have a UTB or JBO would be a satisfactory UTB by now, I think. But let's see. I'm all for it, personally. Subforums like FYAD, despite being hidden to unregistered users, tend to produce the best content on the site (and also the worst, to be fair).