Got a piece of tape on in it here in the picture, wanted to hold in the glass shards. I'd love to get it repaired, but I contacted Nexus and LG support and it sounds like their warranty process is a hole I don't want to dig myself into, probably would end up with a too large bill due to "physical damage" and a phone no more intact than it is now. Not to mention being out a phone for weeks, how can anyone tolerate that? Oh well, I guess I'll just have to take off my nice bumper case and cover up that now uglified back with a more full coverage TPU case.
Update: Well I'm sure many would say I'm wrong and an impact caused it, but I'm reasonably certain I know when it happened. I work on robotic equipment and was doing a calibration procedure tonight when I heard an odd crack. At first I thought it was the machine, but the sound signature was wrong and repeating the procedure didn't cause it to reoccur. I was standing straight up not leaning on anything or having any pressure against that pocket when I heard the sound. It was only later when I was heading home I noticed the odd feel of the back of the phone and discovered the crack. I figure that crack sound must have been it. Shocked me, I've never had a phone crack before, I'm very careful how I handle them. Oh, and I don't wear skinny jeans - I'm build like a defensive lineman, so relaxed fit all the way.
Some people have suggested sending the phone to LG, but they don't have any advance replacement program, and I can't afford to go without my phone for 2 weeks just to get a repair estimate. Got my Diztronic TPU case on order, frankly this is the first phone in years I haven't used one of their cases on, my mistake for thinking the phone would be well built enough that the official case would do the job. I will have to look and see if my credit card has any extended warranty program thing though.
Update 2- So it looks like the damage might be covered under my credit card purchase assurance plan, I have to get an itemized repair estimate to complete the claim though. Hopefully a local place can give me that, like heck if I'm going to send the phone to LG for 2 weeks just for that. Frankly the cost of being without a good phone for that period is worth more to me than the cost of the repair, I'd rather just wait till the part becomes available and pay for it myself. It sounds like they also do replacements if repair isn't feasible due to parts not available, etc. Although the phone isn't currently available either, so we'll see how that goes.
On another note I spoke to one of my friends last night who works for a cell carrier that has many Nexus 4s on their network. She said that 3 employees at the location she works also had cracks on their Nexus 4's in almost the exact same spot. She didn't say they were spontaneous, but clearly it is a weak area on the back of the phone. At least one of them was using a full coverage case when it broke, apparently a TPU case. Alas as regretful the thought of covering such a nice looking back panel is, those who don't have broken backs yet may want to invest in high-impact cases, simple TPU or the bumper doesn't look to be cutting it. Since mine is already broken, TPU should be good enough I suppose, mainly just want to cover up the damage.