Before anyone screams at me I'm just making a point (I am not making a prediction).  I don't believe these graphs have much to do with the irrational exuberance behind the price.  This is simply to make a point about linear growth versus exponential.  Let's say that Bitcoin adoption continues at a linear pace as it has done for several years and the exponential is speculation.  Now here is a 6 month linear graph.  6 months, I didn't have to go back 3 years.  

http://i.imgur.com/xCiE5lN.jpg