Additional note:
I have got this message from the console when I plug in the Arduino.
19/05/14 7:19:46.000 PM kernel: USBF: 20883.941 AppleUSBOHCI[0xffffff800aebc000]::SuspendUSBBus Processing WDH before suspending
19/05/14 7:19:47.232 PM hidd: MultitouchHID: device bootloaded
19/05/14 7:19:47.000 PM kernel: AppleUSBMultitouchDriver::message - kIOUSBMessagePortHasBeenReset.
19/05/14 7:19:47.000 PM kernel: AppleUSBMultitouchDriver::checkStatus - received Status Packet, Payload 2: device was reinitialized