A new survey by cryptocurrency asset manager Grayscale shows that 21 million investors in the U.S. would consider investing in bitcoin. A number of concerns keep these would-be investors from joining the market, however. According to the survey, published Thursday, over one-third (36%) of Americans are interested in buying into bitcoin, but issues such as hacks and the lack of regulation are keeping cryptocurrencies from reaching a broader audience. Seventy-five percent of all investors and sixty-five percent of those interested in investing in bitcoin say crime is their paramount fear.