Bitcoin is tumbling

Bitcoin is down about 9.5% since Wednesday's opening print.
The recent weakness in bitcoin comes following a run up of more than 200% to start the year. Bitcoin's 2017 gains have been propelled by heavy buying from China and Japan .
Recent strength has come on the heels of China's three biggest exchanges resuming withdrawals for the first time since February and Japan naming bitcoin a legal payment method back in early April. Additionally, Russia's largest online retailer began accepting bitcoin even though has Russia said it wouldn't consider the use of the cryptocurrency until 2018.
But, the big gains have created some skepticism as of late. Billionaire Mark Cuban called bitcoin a "bubble" as the cryptocurrency hit its then all time high on June 6. " I think it's in a bubble. I just don't know when or how much it corrects. When everyone is bragging about how easy they are making $=bubble," Cuban tweeted.
About a week later, Goldman Sachs head of technical strategy Sheba Jafari wrote bitcoin was looking "heavy" and due for a drop to as low as $1,915 before seeing a rally. It put in a low of $2,076 before rallying to almost $2,800.
There still remains one big unknown. Back in March, the US Securities and Exchange Commission rejected two bitcoin exchange-traded funds . It has since taken public comment on its decision regarding an ETF started by the Winklevoss twins, but it has not made an additional ruling.