Or, an illustration of why marketers are charlatans who make up pseudo-math to give a false appearance of rigor.
Lets begin by searching on the keyword string "VIRAL COEFFICIENT" - all the top results have to do with Internet viral marketing. Now if you were actually using something like a coefficient in any kind of serious way you'd be deriving it and building it into an equation. Lets try searching on the keyword string "VIRAL COEFFICIENT" EQUATION - all the top results are from the natural sciences. I rest my case.