Do you mean it IS normal wear? Most warranties cover everything except normal wear (tire tread, wipers, etc). If wheel bearings normally wore out so soon, they'd have a point. But since they don't, then a bad part should be suspected (unless they can prove that the owner did something wrong to the car).

I'm just saying I'd make a stink about it and call around to other dealerships or to Mini corporate. Have you checked Mini forums for similar experiences?