“Founded by Jack Dorsey (who also co-founded Twitter), Square began offering its hardware credit card reader, which plugs into the iPhone or iPad’s 3.5mm headphone jack, in May of 2010. It briefly stopped shipping the device between June and August of last year while it addressed a security vulnerability, and then continued shipping out free readers to any who signed up for the service and requested one. Square charges nothing for the hardware, or for the service, but it does take a 2.75 percent cut of each credit card transaction processed using its software.” - × × ×