https://www.cnbc.com/2017/12/04/bitcoin-is-a-dangerous-speculative-bubble-yale-expert-says.html

With the price of bitcoin moving toward $12,000, a top economist on Tuesday sent a stark warning to investors: The cryptocurrency is in a "dangerous speculative bubble."

"This is a toxic concept for investors," said Stephen Roach, Yale University senior fellow and the former Asia chairman and chief economist at investment bank Morgan Stanley.