Great article in B+S
Some might attribute this trend — the increasing use of social engagement by marketers — to the rise of online social media: Facebook, Twitter, YouTube, fan sites, and social marketing websites (also known as private-label media) created by companies themselves. But the trend represents a more fundamental change in marketing practice, linked to insights from social psychology, behavioral economics, and neuroscience and brain research. Every form of interaction between companies and consumers — taking place online and offline, in stores and over mobile devices, in branded content and by word of mouth, and indeed through all direct consumer experience — is now understood to be shaped by the social nature of brands.
Read it all here : The Social Life of Brands
In my book Best! i also argue the point of the Ambassador effect and how it affects the Service industry – you can find the book here