I'm shopping for an old used MBP which I can service and customize...no thanks to the current Apple direction mannaggia! and I see alot of MBP's advertised with large white spots on the aluminum unibody. And I'm saying to myself that if someone wanted to advertise their computer and take many large-sized pictures of it to get top dollar for it, then why wouldn't they wipe it clean so it looks as pristine as possible. My only assumption is that they can't and the grease or oils from their hands have permanently dis-colored the aluminum unibody. But is this possible?