You bring up a really good point. There is definitely a perception gap square needs to overcome before a device like that is trusted by consumers on a wide scale. When someone buys something from a mall kiosk, the mini credit card machine is probably perceived as more secure and trustworthy than a square device on a iPhone.

Theres no doubt that the concept and execution of square is ahead of the curve, but there certainly exists an array of intangibles that may prevent it from gaining critical mass.