The forum is just too big to be controlled by moderators anymore. GAF is past the point where it becomes its own animal. Thats part of running a community as a business. Without a financial sacrifice, a forum run on ads is generally fed with new members until it runs amok for several years.
Yeah, that whole chart showing the inverse relationship between members and post quality is kind of accurate. Granted, I havent' been there THAT long (since late 2002, early 2003), but things are definitely different. I miss the old GAF - probably why I listed so many people, since there are lots of cool folks amidst the distinguished mentally-challenged fellows.
The funny thing about this is that something awful has thousands of members and is probably the best regulated forum I've ever been to. If more forums followed the Something Awful formula, and that is "No bullshit. Always post something of substance." aside for the forums where rules like that don't apply (byob, fyad, your console sucks) things would be better. Likewise, if more big GAMING boards (especially gaf) followed SA's gaming model they would be a heck of a lot better. At SA, if you post a troll for a game/company/console in the main game forum, you're toast. There's a forum specifically for trolling, baiting, and bullshitting. I'd probably be reaching here, but I think gaf would be a hell of a lot better if they had their own take on YCS, banned any sales, console fanboy talk in the main gaming board.
I agree with the stuff about SA. I have an account there, but I rarely post. I just read. There's tons of content over there and I rarely see garbage replies from people trying to ramp up their post count.
I like posting bullshit 
Here's my take. Gaf should have more forums, since its communities have all but exploded.
Gaf main gaming forum: for people serious about their gaming. No bullshit, nothing but news and talking about games. You gain one post for each post in this forum.
Gaf's gaming troll forum: sales data, console trolls, speaking your mind and not giving a shit what people think just to bait them, game trolls. A *not* so serious gaming forum, the counter opposite of gaf's main gaming forum. When you post in this forum, you gain one less post added to your post count. so if you're an avid poster in this forum, people know because of your post count will say -1000, which they will then know to avoid you.
Gaf's online forum: i forget this forum exists but whatever.
Gaf's O-T: for talking about pretty much anything, but joke posts aren't allowed. You would gain one post from posting in this forum.
Gaf's less than serious O-T: This would probably be something similar to evilbore. You could just say what you want, as long as it's not horrible or nsfw, including those goddamn joke posts which are almost always fun to read and make fun of. You would not gain *any* new posts from posting in this forum since it's essentially a *spam* forum.
Of course, it'd never happen.