Tipping Point and Influence

In a recent post about Influencables in Andy Lark's blog, he discussed the Fast Company article where Duncan Watts debunks the Tipping Point concept of social influence.

My comment to his article was:

I agree with you that the two concepts put forward by Watts and Gladwell are not mutually exclusive. What I believe we have with any person that originates or takes up an: idea, trend, campaign, etc. is a weighting or 'factor of influence' on another. This can vary depending upon a number of variable s(and not just the ones measured by Watt, etc.) For example, the tipping point of a particular idea could be a single person, a number of people, or a specific sub-set doing a number of things over time...
the problem (and the fun) is, its always slightly different.

Having read this same article a few times since, I'm less concerned with the opposite ideas of key influncers vs anyone being an influencer.... I'm more interested in why different influencers at different times are able to exert more or less influence and how you would possibly model and report on a real-world scenario. This would possibly have the aim of predicting or changing the outcome. In other words... the "fun" bit.