Square’s stock is up over 200% in the past year; the run up occurred prior to news that the Square Cash app would allow users to buy and sell bitcoin; Square Cash had more than 7 million active users in December of last year; according to the Quartz article, the growth has also been fueled by recent bank partnerships; other successful lines of business include Square Capital which lent out $305 million to small businesses in the fourth quarter of 2017. Source