Somebody dumped 7k BTC and drove the price for a moment way down to 300. Who the fuck is dumping all these BTC?
US government, the Illuminati, Free Masons
But seriously, it could well be someone well stocked in bitcoins who is panicking right now. They bought high, far too high and can't take the pressure any more. For all we (or anyone else) knows bitcoin could be sub $100 next week.