Well, the main problem is that people don't care how organized you are. Deciding what should be a forum is not taxidermy, and if you over classify people will just get confused and post about their problem wherever they want. Probably in some place that more people actually read. A new forum should actually make the site more usable, if anything, because a certain subject is a frequent distraction or the threads are moving too quickly down the page. So I come down on it thinking that unsolicited suggestions just aren't welcome; you don't need input to solve these kinds of problems. If a forum is too busy, it shouldn't be too hard to figure out what people are interested in and where the subject should actually go.
Too many new forums could also change our response time. You should care about that. At the time of this writing, guests (people who can't post) outnumber members by 98% (6 members out of 321 users). It would be different if we had hundreds of members logged in at all times, but all you have to do--even today--is post in a lesser read forum and you have to wait days instead of minutes for a reply. It makes the forum unusable in a completely different way.
Some more thought from the people pitching ideas would make these threads less tedious.