The XperiaBlog reports that a number of users who have tried to take advantage of the Sony repair centers have been turned down by the company, because of the "illegal unlock" of their phones' bootloaders. The bad thing here is that Sony wouldn't even repair factory defects like the yellow tint found in the screen of the Xperia S. How convenient! This move is extremely surprising, considering the fact that Sony itself is providing the bootloader unlocking tool.
Truth be told, the manufacturer does warn its customers on its website that their warranty may be voided if they use the tool:
"Please note that you may void the warranty of your phone and/or any warranty from your operator if you unlock the boot loader."
However, if it "may" void the warranty, that means that in some situations it wouldn't void it. Unfortunately, Sony hasn't bothered to provide more details in order to make this whole thing somewhat more transparent for its users. Well, it looks like in 2012, some companies are still sticking to making vague statements, in an attempt to avoid responsibility and save a few bucks along the way. So, don't be fooled by the fact that the bootloader unlock tool is officially offered by the manufacturer - apparently using it is not "legal".
We've reached out to Sony for more info, and will update the post should we get a reply.
source: XperiaBlog via AndroidAuthority