the volatile nature of bitcoin is because it is a relatively new currency. as people will get aware about bitcoin and adopt it, bitcoin value will get stable. i dont see any possible reason for it to go down to 0 usd. as bitcoin is only widely use currency. as bitcoin will improve the value will get stable.
this is a clear explanation that there is no reason that bitcoin will go to zero...another imposible reason is that cause bitcoin going to zero is if electricity and internet in the world is shutdown, but i think it is imposible