"Q: Are ID cards either philosophically or pragmatically justifiable?
"A: Emphatically no. A requirement for every citizen to carry a device that enables the authorities to demand immediate information about them dramatically changes the relationship of individuals to the state, from being private citizens to being numbered conscripts. An ID card or device (technology will rapidly supplant plastic cards because the latter are too easily lost or stolen) is a surveillance instrument, a tracking device, like a car number plate or the kind of tag punched into a cow's ear." (via No2ID)