Why I'll never buy another Sony product
Sitting in my front room, I can see a Sony amplifier and a PS3. Over the years I've owned many other Sony products and always thought them to be reasonably priced and good quality.
I recently wanted to upgrade my Nexus 4 and after checking that I could install Cyanogenmod on it, I plumped for the Sony Xperia Z2. My brother has a Z1 that I flashed with CM for him and he loves it. The handset I bought was previously SIM locked to O2, so I got it unlocked and debranded it by flashing Sony's stock ROM for the device.
What's a bootloader?
In order to flash a non-stock ROM on a phone (one with a different kernel), you need to be able to unlock the bootloader. The bootloader controls the loading of the kernel. The kernel is the piece of software which provides access to the hardware to every other piece of software on the phone.
Bootloader allow unlock: NO
Unlike every other Android handset manufacturer, Sony have a magic permission that can be set by the carrier (in fact, it's set by Sony at the carrier's request) which encrypts the bootloader and forbids unlocking it and therefore the installing of any other kernel and consequently any non-stock ROM. This is the dreaded "Bootloader allow unlock: NO" - Google it to find plenty of angry Sony phone owners going back the last 3 years - I wish I had.
There is no way to change this permission to YES. Search online, everyone who has ever attempted it ends up in a loop of the carrier blaming Sony and Sony blaming the carrier. Customers end up furious at being told what they can do with their hardware. Of course, you only find this out AFTER you've bought your expensive phone.
I contacted Sony's Xperia customer service team and after explaining my problem carefully, they responded after 3 days to tell me that I'd void my warranty and I should use Sony's bootloader unlock page - the one that you can only use if you don't have this ridiculous allow unlock permission set to NO.
When I pointed out that they hadn't read my original message and I couldn't do that, they pointed me to XDA - the first place I'd look for anything before going to a manufacturer. Which, of course, I had. A quick search will show you that XDA can't help since it would require them to break Sony's encryption keys for the bootloader.
I responded and told them exactly what I was going to do - get rid of the phone and never buy a Sony product ever again. That's what I've done and will continue to do. This includes the TV I was eyeing up and the PS4 I almost bought. Never again, I vote with my wallet. Fuck you Sony.