The theory of social proof or Informational Social Influence is a psychological theory that attempts to explain the behavioral patterns of humans. In essence, it states that when a person does not know how to behave in a given situation he/she will look to other humans for guidance on the correct behavior. An extension of this theory, is that if the group of people who are performing a certain behavior are perceived to belong to the same or similar group, then one is more likely to conform to the groups behavior than if one does not identify with the group.
Now what does this have to do with social media? Let's look at Digg for a minute. Today (like most days) Digg is loaded with niche stories that focus upon technology and funny offbeat news stories. Obviously, this reflects on the audience of Digg (young, male, liberal, tech-focused) but is information social influence not at work on Digg and all other social media sites.
Upon landing on the Digg homepage, the top ten"dugg" stories are displayed to the user. Presented with these stories and seeing all of their votes, it is highly likely I will view at least a few of these and perhaps Digg them as well knowing that many other users found them useful and/or entertaining. This is the same basic principle for all social media sites. Users are relying on others to present them with information that may be interesting to them. This is all well and good because it allows us to sift through irrelevant information rather quickly. But what happens when this theory is used to trick users into thinking information is relevant to them. For example, a site could establish itself as an expert (Google organic rankings) through keyword optimization when it may present nothing new on the subject it portends to be an expert on. In life our radar for people abusing this theory is finely tuned through years of use; however, on the internet, our radar is still being tuned and the dupers are ahead of the curve. How many times have you searched a term in Google, clicked on one of top results and been brought to a page designed to generate ad revenue through page views but has nothing to say on the subject you searched.