[Sony Ericsson Xperia Mini, Mini Pro, Xperia Pro, A] melander:
Just want to share this to all Sony Android phone owners...

...this would definitely answer all questions about warranty and unlocking bootloaders...

http://www.phonearena.com/news/Sony-refuses-to-repair-phones-with-unlocked-bootloaders_id32812

If you are a Sony user and plan to unlock the bootloader of your handset using the official Sony tool, you may want to read this article before you proceed. Apparently, Sony Mobile is refusing to repair hardware problems of users' handsets with unlocked bootloaders.

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.

And here is a response from Sony...

http://www.phonearena.com/news/Sony-explains-why-using-its-official-bootloader-unlock-tool-voids-your-warranty_id32972

You probably remember a story from a few days ago in which we told you how a number of customers ended up surprised that their warranty is voided due to them using the official bootloader unlock tool by Sony. We then reached out to the company in an attempt to get more information regarding the way Sony treats those devices, which have had their bootloadrs unlocked. Basically, we wanted to understand why a user's warranty is voided when they have used a manufacturer-provided tool. Our desire for more details was also intensified due to the somewhat vague statement found on Sony's site, which reads: "Please note that you may void the warranty of your phone and/or any warranty from your operator if you unlock the boot loader."

We now got a reply, and we have to say that we really appreciate the friendly and helpful attitude of the company regarding this issue. Here's what Sony Mobile's PR Manager had to say:

By the looks of it, Sony is more concerned with users flashing a custom ROM, rather than simply unlocking the bootloader. Still, the official also says that known issues (like the yellowish tint on the screen of the Xperia S), are OK and should be covered by your warranty, even if you've used the tool, yet, some customers complained that their warranty wasn't honored. We guess that it will simply depend on the repair center that you visit, or even the person that will examine your phone. At least, one thing is now certain - if you have unlocked your bootloader, you still have chances of getting repair service, but don't count too much on it.