Duncan Watts also happens to be the author of the book "Six Degrees: The Science of a Connected Age", principal research scientist at Yahoo! Research and is a well know critic of 'The Tipping Point' philosophy of influence.
Watts believes that:
social connections are so complex and consumer trends so random, that there's no way for marketers to effectively rely on select groups of influencers to quickly spread a message.
But in my opinion Mr Parsons is correct in his comments about the online influence model being very much alive and of great benefits to companies . This is reflected in the diagram from Tom O'Brien, showing how the online influencers drive others. However he just talks about this in the product marketing sense, but there are other aspects to consider such as reputation, brand, etc.
There is no doubt that online influencers are faster to engage and respond that their off-line cousins. However speed is one thing, quality and impact of that influence are different factors entirely.