Interesting post. I think we have covered it a few times before, but I don't feel like hunting for duplicates, I think engaging users in fresh conversation on such topics in Meta is more important than pointing them to what has been said before. Not like this place is high enough traffic to worry about the odd duplicate.
I won't answer your 3 questions directly (well; yes, everyone, not many) but rather discuss a few things about this site which might well result in a few insights why I genuinely think that Ask Different really is different from most of the other SE sites.
Let's go to other sites first. Here, for example are a list of a few other other sites I use; Bicycles, Arqade, Science Fiction & Fantasy. I use those sites differently to how I use this one (even before I was a Mod too) - those sites are centred about topics for which the majority of users share not just a common interest, but a common passion. For many of the other more IT related sites (Ubuntu, Super-User) those people too are there not just because they have a problem, but because they have a passion for their subjects, or in the least for the technical IT sites are at least skilled and knowledgeable enough to be able to participate.
Now, with Ask Different, things are different. We don't have such a well defined audience of people (either passionate or highly skilled). A lot of our users are here not out of a passion for Apple, but out of frustration due to not being able to do something as a normal everyday person. And that something is such a wide remit. We are here to discuss "Apple", the company and anything it's name can be loosely associated with. And these days, that covers so much stuff:
iPods (from nano to Classic via Touch)
Peripherals, Mice, Keyboards etc
Backup Systems (Time Capsules)
Accessories, from covers to cases to docks etc
And these are just the first party hardware topics Imagine if I bothered to create a list of the software topics, everything from Apple Script to ZFS...
This is the key, our focus is so overly broad that while we can and do have a core membership of highly skilled, experienced, and generally perceptive users, our core membership consists of people that bought something in a shop and can't get it to do what they want. And basically, most Apple stuff these days is by and large a commodity product.
It's the difference between having a site revolving about engine tuning and performance upgrading etc, and one for "Ford". We are guaranteed to get the dumber questions, the ill-informed users, the poorly thought out content. It's just the nature of the massively wide audience we have. Other sites take the cream off the top of their particular areas of interest, and gather them together to form a community. We simply take in randoms off the street, people who aren't here to stay here, but people who want to get in, get help, and get out.
Now is this a problem? Yes in many ways, I doo feel our participation levels and community feel seems lesser than many of the other sites we use
Who's burden is it? Well, it's everyone's, but being practical it's really (and unfairly) on the Mods, the High Level users, the Long Term users to try to corral everything into something like quality content, and we simply don't have enough of those as a percentage of all users like other sites do.
What can we do? Keep calm, and carry on.
As an aside, the first link you direct us to about the Terminal problem, I think is actually a good question. It's a genuine problem, well described with enough info to ensure it get's a proper answer. And I suspect that is where some of the frustration behind your question comes from (good frustration, expressed properly, not having a go here). You and I probably know where to look or how to have a quick Google to fix that in seconds. You're obviously a skilled and experience IT guy. But the OP? Chances are he's a guy who bought an iMac after loving his iPhone, has played about in Terminal so see what it is and such, maybe fiddled with settings, and now has gotten stuck. He's just a guy off the street with an IT problem. He's not an IT guy on an IT site participating in an IT community.
It's a tough one, and hits at the heart of the biggest problem with this site. I don't see a fix.