Investing.com - What's a cryptocurrency investor to do?It's one thing when a traditional investor like Warren Buffett calls out the perils of digital currencies, but quite another when it is a major player in the industry doing it.It happened not once but twice,Ethereum founder Vitalik Buterin posted on Twitter that cryptocurrencies could "drop to near-zero at any time."Ripple CEO Brad Garlinghouse told a tech conference that "most" digital currencies will eventually lose their value. Ethereum and Ripple are the second and third largest cryptocurrencies based on market capitalization. Both men also acknowledged the volatility of cryptocurrencies, though neither actually said investors should not invest in them.The comments coincide with a S&P Global Ratings report concluding that retail investors would "bear the brunt" of any cryptocurrency market collapse.