I agree. For bitcoin's growth, I like the model advocated by rpietila: an S curve, where in the early stages, price grows exponentially, with lots of superimposed noise. As time progresses, we should expect the noise (the fluctuations around the trendline) to decrease. Past data fits this model, with a doubling time of 3 to 4 months. But at some point the growth decelerates and stops. Where, and when? The data so far does not indicate even a hint of deceleration -- in fact, even with the decrease in price of the past few days to $700 (right now), we are still way above the price predicted by the trendline (around $300 ish), which means that we probably still have a long way to go.

All of the above assumes that there are no black swan events or major unexpected developments. The statement by the Chinese government that bitcoin is a commodity not a currency, btw, does NOT count in my book as particularly unexpected. I mean c'mon, what did we really expect them to do???