I've got roughly 30k miles on the bike. The rivets that hold the outer part of the rotor to the hub have all expanded out. There's about 1/2 inch or more of play so it makes a grinding noise when I ride slow.
It was supposedly replaced at 15,000 miles due to a screw up by the person installing my tire. They supposedly replaced the entire wheel and rotor assembly because they took huge hunks out of the wheel.
It always made a funnny noise every so often when riding and squealed like hell sometimes. I couldn't find anything visibly wrong with it until the pads wore down enough to give it some play and when I went to stop one time, the rear wheel shuddered so bad I thought I was going to lose control. No one has seemed to have seen this happen before so I don't think they replaced the rotor and somehow messed it up by banging on it when they were either taking the wheel off or putting it on.