It just seems a bit odd, it's always a pain to remember which category certain anime are posted under and when the website is laggy it's even harder to find. It also seems to be a bit counter intuitive, almost like you're downgrading certain series with little rhyme or reason (certain shows like Spice and wolf have a huge number of posts and still are located in the lower tier. I'm sure there is a reason for this, but in the end I'd suggest having a section containing every anime, if there is still a need to direct traffic to the bigger animes like One Piece there can be larger brackets (like on the main page) for them in the overall section.
Just my 2c.
Alphabetical categories might be a better solution. Having all the show forums in one massive section can still lead to other shows getting ignored.
Fan Favorites is probably intended to highlight shows that have performed exceptionally well (Ouran, Dragon Ball), and shows with mainstream appeal (Afro Samurai, Panty & Stocking)