> Forums/Q&A involve waiting for answers within a permitted-QA context.

The question primes the brain for the answer. You can use that socratic lead structure without going with a traditional Q&A wait-and-pray approach (ala Stack Exchange, Answers.com, Yahoo Answers, and so on). It does require a specific system design though. You can induce and control the Q&As around a topic, you don't need to wait. Doing it intentionally and rigidly, in some cases leads to a far superior system, as opposed to the chaos and quality problems of junk filled Q&A sites like Yahoo Answers or Answers.com. In the history of the Web only one major traditional Q&A site has ever gotten it really right over time, that's Stack Exchange (and we'll see yet if their commercial interests don't erode what they accomplished, as the VCs demand their exit). The track record is abysmal because most Q&A sites are beholden to an inherently bad approach: relying heavily (and allowing) on large volumes of people with no specialization or passion for a subject to ask & answer questions (so you get a lot of low quality drive-by answers that have to be moderated away or tolerated). It's the equivalent of walking into McDonald's and expecting a five star experience, and then being surprised when it's not (when it was obvious all along exactly what was going to happen, only one outcome was possible). wikiHow, as one example, has persisted (while nearly all other how-to sites have died off in the age of Google Penguin/Panda/etc) at a modestly sound quality for so long, because they set the hows, rather than just waiting around for junk how-to questions to be asked and answered in a mediocre fashion by low quality drive-by contributors; and they accept a lower level of commercialism and volume. wikiHow worked because they do hows in a similar way conceptually to how Wikipedia does topic pages (it's all rather preordained down a strict funnel, instead of wild flailing). You can do the same thing in other ways in the Q&A segment.

Not to mention of course in most cases a site's desperation for ad clicks and page views causes them to intentionally allow volumes of low quality trash to populate their Q&A systems (what Quora turned to as it became obvious they couldn't fulfill their valuation otherwise), instead of aggressively pursuing only quality. Quality in the knowledge space is very slow, it takes enormous amounts of time and requires aggressive, consistent, persistent moderation. It takes a long time to build a high quality knowledge culture that self-reinforces, self-protects.

I don't personally believe all questions have merit, quite the opposite. This is another core flaw to the typical Q&A site. Few questions - in the grand scheme of all likely human-generated questions - have much wide merit. Numerous low value Q&A sites have overwhelmingly demonstrated that to be true over time. It's millions of people walking by, spitting on the sidewalk, and calling it art.

> Therefore slow, not guaranteed, indexed chronologically not logically

Slow is ok. Very few things of great value are built quickly, that's true today, and it has been true throughout history.

Guaranteed you can heavily influence, by adding source requirements and restricting contribution (stepped barriers to contribution, and site-culture acting as an enforcer). I use a system that adds more friction to contribution than Wikipedia for example (I don't directly compete with them, I'm not building another encyclopedia), however there are aspects to my system that play to that approach better than it would on Wikipedia, so it evens out. You also want to build a culture that regulates low quality contributions, including brief / incomplete; you can do some of that technically, however you ultimately need a human culture involved at the center, I believe it'll still be another few decades at least before AI can do it effectively enough top to bottom.

Indexing order can be influenced and dictated by editors into a logical structure, although this buckles under duress on the standard messy high volume Q&A sites with millions of people spitting on the sidewalk. Those are too disorganized, unstructured for that bottling / silo approach to work. The typical Q&A site is a landfill; landfills are mostly filled with high volumes of low value trash, you don't want to go in there and try to logically order it; it's a large amount of effort for a small payoff because the content isn't very valuable (does this rotten banana peel go before that one). You have to narrow the Q&As in topic, quality and volume, on the basis that not every question matters. If you believe every question & answer matters as a site, you end up as Yahoo Answers or Answers.com (ie worthless in the end).