I decided to rotate my tires this past weekend (font to back) and found some unusual tire wear (to me at least). I expected some excessive wear down the middle since I realized that I had been over inflating my tires and probably some wear on the inside from neg camber. On the drivers side I was surprised that the front tires showed more inside wear than the rear. On the passengers side it was basically the same but I didn't expect this:

It looks like chunks of tire has been worn off on the inside of the tire. This is the rear passenger's side and no other tire has this problem.

So guys what's the problem? Toe-in toe-out?