The high volatility is a major risk. People who accept BTC as a means of payment are often in the red when prices are falling. Government regulations represent another risk.
Well, there are too many factors of risk in bitcoin but I don't see the volatility as the major risk, because most likely holders will not be losing their capital amount since no one will be selling bitcoin at the lowest price. The risk of bitcoin that I afraid of are those big holders or big players in the market, once all of them were have the same idea to sell their bitcoin, that could be a huge dump possible. However --for now, let us not think that matters, enjoy your life because that is too short.