There’s a recent article in the New York Times about how “likes” and “up-votes” are contagious. http://www.nytimes.com/2013/08/09/science/internet-study-finds-the-persuasive-power-of-like.html
“Likes” and other user feedback systems are at the core of what is called the “Web 2.0”, a transformation of Internet culture (which is like saying, culture) that started around 2006.
A couple of years ago I wrote a book on argumentation (still unpublished) in which I claimed that likes, user feedback, and user ratings are the new form of argumentation. That is, the argument that if many people find something good then that must be good is the main topos of the current era; a purely quantitative form of argumentation. I quote from the article:
“Hype can work,” said one of the researchers, Sinan K. Aral, a professor of information technology and marketing at the Massachusetts Institute of Technology, “and feed on itself as well.”
The first person reading the comment was 32 percent more likely to give it an up vote if it had been already given a fake positive score. There was no change in the likelihood of subsequent negative votes. Over time, the comments with the artificial initial up vote ended with scores 25 percent higher than those in the control group.
“That is a significant change,” Dr. Aral said. “We saw how these very small signals of social influence snowballed into behaviors like herding.”