The North Carolina DOT Division of Motor Vehicles requires that all motor vehicles registered in the state be covered by an automobile liability policy and that the insurance must remain in effect with continuous coverage until the registration is terminated.
So accordingly to the wording of the Vehicle Financial Responsibility Act listed above, it would appear that NC requires the car and not the driver to have insurance on it. If this is the case and you are a non-owner, when driving other people's vehicles you would need to make sure they are properly insured.
If you are going to frequently borrow someone else's vehicle your friend should contact their insurance company to make certain that you will be covered in the event of an accident. Their insurance company might want to add you as an occasional driver.
To find out for certain if you must carry insurance to drive others cars even if you do not own a car, contact the NC DOT. If you do need auto insurance, you can get a non-owners policy to cover you or if there is a certain car you want to cover in some states our partner Esurance has coverage you can buy, even if you do not have insurable interest in the vehicle.