I heard someone either deliberately (shorting the price at the same time on other exchanges) or by accident placed a 30M sell order at market price on GDAX. In 2013 setting buy and sell orders 15% above and below market price was a good strategy. Thats mainly how i turned <1 BTC to 14+ BTC. I have never had that kind of returns since and its a lot harder nowadays. I only have <0.1 BTC as i sold the lot at $750:)