" A recent experiment nicely demonstrates the power of random first moves to generate cascades.6 Researchers worked with a website that aggregates advice on restaurants and other services. Users post comments, and other users add an up- or down-vote. In their experiment, the website randomly chose a small fraction of comments and gave them one artificial up-vote as soon as they were posted. They also randomly chose another small batch to get a down-vote. The positive up-vote significantly increased the probability that the next user also gave an up-vote, by 32 percent. After five months, the comments that had received one single artificial up-vote at the beginning were much more likely to get a top grade than those that got a single down-vote. The influence of that original nudge persisted and grew, despite the fact that the posts had been viewed a million times. "

― Abhijit V. Banerjee , Good Economics for Hard Times: Better Answers to Our Biggest Problems