"Mark Cuban has attacked Bitcoin on Twitter, claiming it is not a currency, it is a bubble, and that the whole system of valuation concerning it is wrong. But is he right?" 
https://futurism.com/mark-cuban-asserts-that-bitcoin-is-not-currency/

His comment caused the Bitcoin price to drop before it hit $3000.  He said Bitcoin's increasing price now is a bubble.  What do you think?