The good news is that Yellen does not seem to view the cryptocurrency as an imminent threat to the U.S. financial system.
https://bitcoinist.com/u-s-federal-reserve-chair-janet-yellen-downplays-bitcoin/
Good to read this kind of article, it is not really a problem but the real problem here lies on the people who uses Bitcoin to perform bad actions , illegal actions, Fraud and Fake ICOs. We still need to wait for the development of this story, maybe this is just another story to pump up BTC and then later on someone will provide FUD articles. https://bitcoinist.com/u-s-federal-reserve-chair-janet-yellen-downplays-bitcoin/