Share your experience!
So, another self-cracked back glass on a Z2!
Phone is brand new. Used it for some browsing, put it in my pocket, took it out shortly after again and the back glass was completely shattered. I took the phone to a repair shop (not Sony) and the technician agreed that since there was no breaking point or other indicators that the phone had been dropped, it must be an "internal thing."
But surprise! Sony disagrees.
Basically I got told by customer support that a shattered glass will be considered a user fault no matter what.
Think about that for a second: Sony sells me a faulty product. It then breaks due to poor build quality and it is my fault regardless of what documentation and examination of the unit is provided (together with all the evidence from other users experiencing the same).
I am going to contact the equivalent to the "Watchdog" show on BBC here in Denmark to hopefully have them investigating this. This is NOT how you take care of your customers.
I've just sent mine off.
Put my phone on charge, face down overnight whilst I was asleep - woke up with two horizontal cracks on the back plate.
Gutted.
Sorry Malt1977, but I don't buy that. If I can't have my phone in my pocket (in normal jeans) without breaking it, something's wrong with the design of the phone. Period.
It really is a bit of a catch 22, we can't prove that there is a fault with our phones, but then Sony can't see what use our phones have. My advice would be to push back on them again (it's worth a try) but maybe mention you'll take it further. Some people have done this with a degree of success, but ultimately, Sony have the last word.
Good luck though, and let us know how you get on.
Mine cracked after 4 days. I did not put it in my pocket it just cracked. 
You need to either return your device to the place of purchase or contact Xperia care http://www.sonymobile.com/global-en/support/contact-us/
I bought a Xperia Z2 in August 2014 and had to change the back glass already 2 times due to cracks. Now it cracked again. I am living in Africa and the repairs were done locally, against payment evidently.
I have been treating the phone like a raw egg.
Very unpleasant!
How can this back glass be of such bad quality - with Sony.
I can't beleive it