Microsoft co-founder Bill Gates is no fan of cryptocurrencies, which he says have become a vehicle for crime, and in some cases can result in people's deaths.
During a Reddit AMA on Tuesday, Gates said the anonymity of the web means cryptocurrencies can mask money transactions. "I don't think this is a good thing," he said.
That same anonymity can facilitate tax evasion, money laundering and terrorist funding schemes. "Right now crypto currencies are used for buying fentanyl and other drugs," he added, "so it is a rare technology that has caused deaths in a fairly direct way."
To be clear, the anonymity isn't perfect; for instance, law enforcement and the IRS have been using software and experts to track bitcoin transactions. Nevertheless, cryptocurrencies have certainly become a favored tool among criminals to move money.
One Reddit user was quick to point out that U.S. cash can be used to buy drugs anonymously, too. But in response, Gates said: "Yes -- anonymous cash is used for these kinds of things, but you have to be physically present to transfer it."
Gates is the latest famous figure to weigh in on the cryptocurrency craze, which has drawn polarizing reactions across the business and tech world. His friend billionaire Warren Buffet has also warned investors to steer clear from the digital currencies.
Others are more curious. Last month, Facebook CEO Mark Zuckerberg said he was interested in studying the "positive and negative" aspects of cryptocurrency technology. Meanwhile, Asian technology firms Line and Rakuten have unveiled plans to actively dive into the market.
In the same Reddit AMA, Gates revealed that he's particularly excited about robotics and virtual assistant software.
"The most amazing thing will be when computers can read and understand the text like humans do," he said. "Today computers can do simple things like search for specific words, but concepts like vacation or career or family are not 'understood.' Microsoft and others are working on this to create a helpful assistant."
Gates was also asked if he'd ever run for U.S. president, to which he said no. The Microsoft co-founder said he can accomplish more as a private citizen through his foundation, which is focused on solving poverty and disease.
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