Modeling Viral and Marketing Growth, Part Two

Picking up from last week's post, the first thing I want to show is that I kinda cheated last time. To see what I mean, let's look at Rahul's original chart:

In Rahul's model, if we start With 5,000 initial customers and a viral factor of 0.2, we end up with 6,250 customers and we never get any more! But in my model from last week, if I use 5,000 and 0.2, customers keep piling up exponentially: