In the beginning you write about aggregation of judgments, but later you turn to something else:

When you're stuck with a question, whether personal, professional, or academic, it is often effective to turn to the hive mind for suggestions.

The hive mind can be useful for both of these things, but they are distinct and should be kept apart. The first idea is the one most famously discussed by Condorcet, namely that if a number of voters are on average at least slightly more likely to be right than wrong, then the probability that the majority is right goes to 1 as the number of voters goes to infinity. Generally speaking, if group's are not systematically biased, then their aggregated judgment tends to be (if the aggregation procedure is reasonable) better than the vast majority of the individual voter's judgments.

The other use of the hive mind is rather that as you ask more people, then the probability that at least one has precisely the kind of knowledge you need increases. In this case, the fact that some people are completely ignorant doesn't hurt you (though it doesn't help either), since all you're looking for is this one person who has the kind of knowledge that you need.

I'm working on this at the moment. My suggestion is that people have not paid sufficient consideration to the set-up. In order to make best use of "the hive mind", you need to give people incentives to give sincere votes, and weigh the more reliable voters more heavily. Prediction markets is probably the system that does this best at the moment, but they are impractical in many situations.