One thing he does not mention which is very important is that an exponential is self-similar.  What that means is at ANY point on the graph, plotting just the prior values (at a visible scale) looks like a bubble.  For example, over the course of a year when 2 rats become 100, the last 50 rats were born within a few weeks.

It is only when the curve starts to flatten out that you can tell where the vertical portion was...  So Dec might have been the vertical adoption, but if BTC ends up at 100billion valuation,  this "vertical" will look like an anthill like 2011 does today.