As I shared in another thread:
Business-wise the forums are effectively irrelevant. Less than 1% of my blog readers ever visit the forums. The forums chew up a lot of bandwidth and resources because VBulletin is very server intensive, but the blog's traffic dwarfs the forums' traffic.
The forums aren't a money-maker, so paying someone to admin them would just make them more of a drain. Even so, I was heading towards doing that, but in retrospect I'm glad I didn't.
I didn't start or end the forums for business reasons, but from a business perspective, ending them will free up time and energy for other pursuits.
It may seem like this forum community was huge, but the total number of members who've registered here after 5+ years is less than one day's worth of blog visitors.
The main reason these forums because so popular is because the blog kept feeding them traffic. Without the blog, these forums would have been a ghost town.