This article by Greg Daniel from KPMG really gets to the point. It reinforces why social media and word of mouth referrals are so powerful.
“According to Nielsen, only 16% of people are influenced by advertising they see on the Internet while 84% are influenced by what people tell them on social media. While the growth in online advertising is dramatic – it is still advertising! Today, the newest thing in marketing communications is also the oldest in the world: word of mouth”