It is widely believed that traditional media--radio, TV, newspapers, magazines--shape our conceptions of reality. The content discussed on news programs, advertisements and opinion articles can all influence our conclusions about society.
There have been a number of studies arguing that the media control doesn't necessarily influence our daily decisions, but it does shape our overall perceptions about society and culture. This includes studies by Eibach, Libby and Gilovich in 2003, Iyengar and Kinder in 1987, Gerbner, Gross, Morgan and Signorelli in 1986 and many more.
If you think about it, traditional media can't help but influence our perceptions of reality. Even if every media outlets on all platforms was completely objective they would still influence what people thought about by deciding which stories to discuss and publish.
I bring all of this up to make a point. As social media grows, traditional media's influence over people will continue to wain. The public now has a mass platform of communication where they can dictate the content and the direction of opinion. This is no more apparent than it is when you consider that Iran protests were the second most discussed topic by influential Twitter users in 2009.
We often say social media puts power back into the hands of the consumers, but social media goes beyond the consumer/brand relationship. Social media puts the power of perception and reality into every individual that wants to take the time to evaluate it.