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My housemate's MacBook is exactly the same. Cracks all around the outside and on the top wrist rest part (which she has had replaced at least once already).
 
I spoke to the nearest official apple repair centre, and this is what they said.

Hi
Apple will not replace bottom cases in warranty, you can speak to Apple and
ask if they will make an exception.?
If you haven't dropped it, and it looks like a hairline crack to me (same as my hubby's MB) then I cannot see why they wouldn't fix it. It's in warranty and has only happened after a short period of time. If it was my MacBook I would go insane at them to fix it, especially after that short period of time.

I, however bought my husbands MacBook 2nd hand and already had the hairline crack which as you know does affect performance so can't get it fixed.
 
Sigh.

If anything has ever made me want to go PC its apples customer service.

I know that this doesn't make you feel any better with your current problem, but Apple's customer service is much better than any customer service of a PC maker (dell, HP). This is one of the reasons that apple is so expensive. Don't throw in the towel yet, because we all know that Apple is a superior product. Be persistent and you'll get that fixed. BTW, did you drop it or bump it?
 
Apple's customer service is much better than any customer service of a PC maker (dell, HP). This is one of the reasons that apple is so expensive. Don't throw in the towel yet, because we all know that Apple is a superior product.

In my experience that isn't true when it comes to IBM/Lenovo.

It still doesn't excuse apple for making a computer out of a material which would crack that easily.
 
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