Investing in bitcoin was risk in the past when people were new to it and were not having enough faith in it as at that point they had fear of loosing their money in it but now after looking the growth and success of bitcoins I don't think there is any risk of investing money into it.
Well every investment has a risk element if someone is afraid of taking risk it is better for them to not to come to any business. Yes, if someone is ready to take risk than now a days the bitcoin is the most suitable investment with low risk high return factor. If we look at the progress of the BTC in the last two years it seems the most profitable business investment.