See what the Pew Research Centre has to say on this topic, here: http://www.pewinternet.org/2007/12/19/communications-and-social-media/
In previous days, people mostly engaged with others using communications such as radio and television to reach and meet the needs of consumers, but in the modern era, social media always helps to make sure the brand voice is carried out across all media.
Moreover, social media is the only thing that we can find everywhere in the world. These social media masses are like roses without thorns--there is no down side. Social media helps each company point to and promote their products.
Mostly, these masses like and follow industries, not only to be part of a community, but to stay connected to products, promotions and developments.
Social media is always evolving quickly, moving from just a place to communicate to an environment that can help sell and inform messaging.