Sanjay Mehta, Jt CEO of Social Wavelength, gives a simple explanation of the concept of Facebook Edgerank. That concept that creates the filter for any FB user to get a selected range of updates from his friends or brand pages. The same concept due to which only an average of 16% of a page's fans see the page's updates, on their walls. The background of this concept and the concept of reach generator are explained in this presentation.
A video blog version of this presentation has also been uploaded, and same can be viewed at http://youtu.be/0twWXYimUk4