If you planned to hold it for short term then the risk is small, but if you planned to hold it for 10 or 20 years maybe that a bit risky, as we know bitcoin still in growing process so anything can happened, maybe it can grow stronger or maybe can be replaced by other coin, but I more believe that bitcoin will grow stronger in future, that is why I think holding bitcoin as investment is a good idea, just don't put all your wealth in bitcoin, invest in different form is better
its good to hold for short term but i think its more good enough if you hold it for at least 1-2 years from now because we are know that bitcoin is something new in our world and many people predicted that bitcoin has a good chance to be future payment and money for future so i think at least i can save my bitcoin as investment like many other people. i am agree with xuan87 said that don't put all of our wealth in bitcoin, we need to spread it into many investment so if our investment is grow, we can get profit.