Either the piston isn't retracting as it should, ir the whole caliper is failing to move as it should, causing the pad to drag and wear both pad and rotor.
The rotor takes the spark generated by the ignition coil and distributes it to each spark plug wire as it rotates on a shaft inside the distributor cap. It is subject to constant spinning and voltages that will wear it out in time. A bad distributor could cause premature wear.
To wear....
Normal wear on the bearings inside.
First I would have the rear rotors removed to inspect the emergency brake shoe's and rotor for wear. Sometimes people are known to drive with the emergency brake engaged which will wear the shoe and rotor. If they are still within specs, there is an adjustment on the shoe's
A bad rotor would not necessarily cause a bad vibration as it would most likely create a noise and wear your break pads down unevenly. It could be as simple as an unbalanced tire or a warped rim. Also if your tires are choppy then a vibration can become noticeable. Also a bad bearing or axle could cause vibration (however, it would be noticeable at a lower speed).
You need to have a 4 wheel alignment.
Poor tire alignment will cause wearing on the inside edges of rear and even front tires.
YOU WILL WEAR YOUR PADS OUT PREMATURELY AND MAY CAUSE HOT SPOTS TO FORM IN THE ROTORS. HOTS SPOTS BECOME HARDER THAN THE REST OF THE ROTOR AND WILL CAUSE THE PEDAL TO HAVE A BUMPING FEELING WHEN YOU APPLY THE BRAKES. THE ROTOR WILL THEN HAVE TO BE REPLACED TO SOLVE THE PROBLEM. ALL IN ALL YOU SHOULD HAVE THE PROBLEM CHECKED AND REPAIRED ASAP. BRAKES ARE NOT A GOOD THING TO GAMBLE WITH FOR SURE.
Something may be worn or bent in the rear. Many vehicles require 4 wheel alignment.
Did you have the rotors turned or replaced? If the rotor surface was not resurfaced it can often cause noise, premature wear and uneven stopping.
The distributor handles several jobs. Its first job is to distribute the high voltage from the coil to the correct cylinder. This is done by the cap and rotor. The coil is connected to the rotor, which spins inside the cap. The rotor spins past a series of contacts, one contact per cylinder. As the tip of the rotor passes each contact, a high-voltage pulse comes from the coil. The pulse arcs across the small gap between the rotor and the contact (they don't actually touch) and then continues down the spark-plug wire to the spark plug on the appropriate cylinder. When you do a tune-up, one of the things you replace on your engine is the cap and rotor -- these eventually wear out because of the arcing. Also, the spark-plug wires eventually wear out and lose some of their electrical insulation. This can be the cause of some very mysterious engine problems.
No. That would be friction.