Here's a look at about 10 months of viewership data for a short video that I posted on YouTube and then left for observation.
Notice the long tail pattern for the entire time period. After a period of initial interest the pattern settles down to a lower level. Notice also the Pareto distributions in the fashion of fractals (self-similar patterns).
The onset of each fractal was occasioned by different blogs that briefly featured the video. In many ways bloggers can be viewed as gate-keepers taking us back to Katz and Lazarsfeld's "two-step model of mass communication."
The "Theory of Least Effort" provides one psychological explanation for the fractal pattern. "Marketing influentals" are willing to expend more effort and are more motivated to share what they have found. In the early phase, they make finding a source easier for those who are unwilling to expend the same levels of effort in seeking and sharing.