It looks like Sony is refusing repairs to customers that have unlocked the bootloader on their device. Customers who have sent their device in for repair has had them returned with no work done due to the "illegal unlock" that is unlocking the bootloader. It looks like this isn't the case worldwide, but those sending in their Sony devices to UK and Dutch repair centers are experiencing this. unfortunately relocking the bootloader doesn't work either. As their technicians can tell that the bootloader was unlocked in the past.
For those of you that think this is unfair, on every device that you try to unlock the bootloader on, you see this warning (or something similar):
"Please note that you may void the warranty of your phone and/or any warranty from your operator if you unlock the boot loader."
Yes it does say that it may void your warranty, but you should usually assume that it will just to be on the safe side. But that may part in that warning is a bit misleading. An unlocked bootloader should have nothing to do with hardware issues, like the yellow-tint on the display.
Has anyone else in other regions of the world sent in a device to Sony for repair and had it rejected due to it being unlocked?
[Source: Xperia Blog]