Social proof is a phenomenon known to some as "informational social influence." It occurs in unclear social situations in which people are afraid to make decisions regarding the appropriate response to a situation. As opposed to the "bystander effect," people will often follow the lead of others in determining what to do.
When you find yourself in a random social situation and you begin to classify people based on their current social situation, you are supporting the theory of social proof. A man surrounded by beautiful women is perceived to be more valuable than a man who is rejected by women. Get more information here about the social proof tool.
We tend to make assumptions along the way that affect our decisions about others. Sometimes we are right and sometimes we are wrong, in any way, we are guilty of doing it and that shapes our perception of others. When you're in a theater and someone claps, everyone else joins in because hearing that clap in the first person is a psychological trigger that lets us know that it is good and deserves our applause.
When you consider the great power of social proof, you will begin to see the great value of social proof as a sales tool. When a potential customer sees your product as a highly desired product, they feel a stronger need to buy it in order to have something highly sought after. If you promote products as if you are doing the customer a favor by allowing them to buy your product, they will value it more and be more willing to commit to buying from you.
Social proof is a useful tool in sales, however, its power has the potential to be used unethically and therefore should be used with great care. Remember that at the end of the day, it is his reputation as a salesperson that is really important.