There is always risk in any investment, the risk of lossing or worst case scenario, even can not recover the principal. However, because of the risk, in return a big profilt will be earn once you become successful.
Yeah, there is no single investment that I can imagine that does not come with its own risk and the higher the risk the higher the benefit you gain from it. However, some risk are not always worth taking and would rather be sensible to stay away from them or being careful to play smart when taking them. Getting too greedy sometimes has led some people to the drain while taking some high risk.