I don't like having sectional moderators as most of the time unless its a massive forum with thousands of posts a day then most of the time they will not have much to do really. It is so much better to have global moderators that can just manage all the forums and it also creates less hassle with only having to hire and manage a few moderators without having to find one for every section of your forum
Our office website's forum is pretty small so just 1 admin and 1 moderator can handle it for now. When I was in a forum of horse racing aficionadoes, there were so many moderators - 1 for each board and sometimes even 2, that's aside from the so called global moderators that has the entire forum for their territory. There's also the admin and assistant admin (2 persons). Those "officers" of the forum were appointed just for the position, more on their dynamism and frequency of logging in. But I don't see a need for such many moderators.
Depending on the amount of sections a forum as, will depend on if it needs sectional moderators or not. If a site isn't that big there's no doubt that one global moderator will be able to handle it but as a forum grows and the traffic increases, there might come a time when it gets too much just for one person to manage.