Iphone 3g Cracks after 4 days!

I was lucky enough to score a 16 gig white Iphone 3g from my local Craigslist. The guy was only asking $125 so i offfered $100 and amazingly he accepted. I didnt notice until later when i got it home that the mute/silence button on the side of it was broken and useless. I then consulted Google where i found this to be a fairly common occurence and is covered by the 1 year warranty of the Iphone, so i brought it down to my local Apple store and like magic i had a brand new one!
Whats more it was one of the earlier ones with bootloader 5.08 so i was easily able to downgrade the baseband and unlock it with Yellowsn0w. I only had it 4 days before i noticed these cracks (pictured), and ive never dropped it. Well since i only had it 4 days i brought it down to Apple store again and again they replaced it. Yay! This time i examined a bunch of the 3g's on display at the Apple store and every one that i picked up had some cracks on them somewhere.
This time however the phone had bootloader 5.09 making it impossible to downgrade and unlock (except for special sim cards). So now im stuck with a brand new ipod 3g until they release the unlock for it.
Apple, I love you, Apple i hate you, love you, hate you, love you, etc.