It is not completely unpredictable. It has mostly been going up since 2010 (when it first got a price), and yeah there have been periods of down, but you will must consider that the trajectory has mostly been up, which justifies considering getting some in case it catches on, and then once you get some just continue to buy it... . there is no reason to believe that it has stopped in its overall trajectory to go up, even if there are likely going to continue to be various corrections (and volatility) along the way.