I see various discussions and invocations of crowd wisdom that don't seem to have a good grasp of the subject.

If you think the probability that something will happen is 90% and then you find out that your friend said 30%, what should your new assessment be? What if the average of ten of your friends' assessments was 30%? . . .

Most people would shift their assessment at most halfway toward 30%, to something between 60-90%. But the theory on "not agreeing to disagree" tells us that shifting even further may often be warranted. In this post, we don't weigh in on theoretical arguments at all. Instead we present empirical evidence showing that -- at least in one narrow setting -- there is a clear benefit for almost everyone to lean heavily toward the crowd's assessment rather than one's own assessment, even more so as the number of other assessments grows. . .

Also note that these results are for random groups. If there is reason to believe that your information may correlate with your friends' information, averaging with your friends may be less effective in general than averaging with random strangers.

The emphasis is in the original post, and it is misplaced. What should be emphasized is the last quoted graf.

This old post from almost two years ago explains why.

It seems difficult for some to distinguish between the aggregated wisdom of a society and collectivism, which is almost never wise. We see this in reviews of the work of Surowiecki's The Wisdom Of Crowds: Why The Many Are Smarter Than The Few and How Collective Wisdom Shapes Business, Economies, Societies, and Nations. Surowiecki uses the C word too but in a restricted way.

"Under the right circumstances," Surowiecki argues, "groups are remarkably intelligent, and are often smarter than the smartest people in them."...

As counterintuitive as it sounds, however, the mathematics work so long as Surowiecki's three key criteria - independence, diversity, and decentralization - are satisfied. "If you ask a large enough group," he says, "to make a prediction or estimate a probability," the errors they make cancel each other out. "Subtract the error, and you're left with the information."...

Independence, diversity, and decentralization. Your friends are not likely to be of much help to you, no matter how many friends you have. In fact, the larger such a group becomes the more likely it is to be wrong, and the greater the amount of error becomes. Like minded groups become more radical, less realistic, the larger the groups grow. There is a slim possibility that such a group can help you if you are particularly dim witted or deluded, but you would still be better off choosing strangers for your advisors since they would more likely be diverse, independent of one another as well as you, and hadn't colluded in advance (and so dumbed themselves down).

Your friends may be good advisors if you consciously cultivate a heterodox group. If they are heuristically diverse and have a variety of values and ideologies there may be some tension but will be a more powerful thinking machine. You are likely to improve personally as well over time as you acquire a larger mental tool set by poaching from your friends, and gain skill at listening to contradictory views knowing that it will help you discover truth, even if it is uncomfortable to do so.

If truth matters to you - and I'm aware that this is rare - then collect odd fellows.