In his own reddit AskMeEverything page,
https://www.reddit.com/r/IAmA/comments/80ow6w/im_bill_gates_cochair_of_the_bill_melinda_gates/He answers about cryptocurrency stating
The main feature of crypto currencies is their anonymity. I don't think this is a good thing. The Governments ability to find money laundering and tax evasion and terrorist funding is a good thing. Right now crypto currencies are used for buying fentanyl and other drugs so it is a rare technology that has caused deaths in a fairly direct way. I think the speculative wave around ICOs and crypto currencies is super risky for those who go long.
He isn't wrong in his sense, if the cryptocurrency is to have a future, they should be able to create an environment of trust between themselves and the authorities.
I do not agree if the crypto currency is said to be one of the bad things. Crypto currency is a great technological development. Indeed crypto currency offers several features which are very risky to be used for crime but this is not a bad thing about crypto currencies. The bad is those who use crypto currencies for crime when crypto currencies should be used for more positive activities. The bad is not crypto currency but the user is irresponsible.