is the title of a column by Guy Kawasaki in AlwaysOn. It covers a study on the effectiveness of different kinds of word of mouth. I tend to agree with the results and Guy's comments.
The most effective WOM is by family, friends and colleagues, followed by regular folk and then pundits or those "in the know". If this was not the case, we'd be right back in the days of old media with the control over, or filtering of the message by editors and professionals. Those days are fast fading away as social media asserts itself.