Sites select content that is most likely to generate engagement they can sell to advertisers. Content that is liked turns out to be a poor strategy for that. Content that generates violent reactions of all kinds is more effective. (See also tabloid newspapers.)

Karma is a very poor proxy for post or poster value because it's cumulative.

Example: Stackoverflow has no way to distinguish between a poor post and a good post that's too recent to have acquired many upvotes. Likewise karma provides no useful distinction between someone who has been posting for years and someone who has just joined. (Also applies to Reddit and HN.)

In fact markets are perfect examples of Keynesian groupthink. The goal of most investment decisions isn't to assess intrinsic value or potential, but to second guess how everyone else in the market will estimate their ability to profit from collective average estimates of value/potential.

This leads to investment distortions where investors would rather chase potential unicorns - because of the explosive IPO potential - than invest in unexciting but solid businesses with stable but undramatic growth prospects.