Upvotes and downvotes on Reddit and information cascades

In 2014, a scientist got banned on Reddit for having 5 accounts he used to downvote others’ posts/comments and upvote his own. While five votes doesn’t seem like much when posts/comments can get hundreds or even thousands of votes, we know from learning about information cascades and herding behavior that five early votes can and does make a difference.

We’ve learned that if just the first two people making a choice make the same decision, it can start an information cascade where everyone after also makes the same decision. In this scenario, upvotes/downvotes are visible to everyone and act as a public signal to Redditors of whether a post/comment is good or bad. This is at odds with their private signal, their own opinion of whether a post/comment is good or bad. A Redditor may think a comment is bad, but if the comment has 5 upvotes minutes after it’s posted, the Redditor may start to rethink their belief. Maybe those first five voters were more informed on the topic and had information this Redditor doesn’t. Maybe if everyone else thinks the comment is good, it is rational for this Redditor to also upvote it.

Due to herding behavior, the early responses to a Reddit post/comment can be a good indicator of its popularity down the line. Thus, this scientist is artificially controlling public opinion and affecting the integrity of the social network. If the scientist uses all his accounts to upvote his comment and downvote someone else’s, that’s already a ten-vote differential between the two comments. If people use these votes to influence their own behavior, the scientist is able to control the broader outcome of these comments by simply logging in to his multiple accounts and spending a few minutes voting.

https://www.vice.com/en/article/8qx57x/reddits-favorite-scientist-just-got-banned-for-cheating-the-site