Ok, one serious attempt from someone to sidetrack and confuse the audience. Take a look at the HTC One. Now, Facetime aside (which is irrelevant anyways because facetime at least knows to use the FRONT camera, which the front camera is designed in the center), lets look at how iPhone's back camera compares.
Would HTC One allow you to hold with both hands in horizontal mode so you don't get blurry photos? Yes. (It also allows you to take vertical photos too, look at its placement)
Would iPhone allow you? Nope. You would have to fumble and be careful to flip it back and forth, checking if you have not touched the lens, which means missed opportunity shots. Or go with one hand shaking, blurring the photos.
But seriously, read this statement: NO ONE TAKES VERTICAL PHOTOS if they are serious. Landscape photos are the norm. Why is your monitor on your computer horizontal, not vertical? Why is the movie theatre horizontal and not vertical? Why is the land on the ground horizontal and not vertical? Common sense. If you like facetime, it uses the FRONT camera. And who says it has to be vertical for facetime? I would prefer others to see more of my background like a regular photo.
This same design infected the large iPad. On such a large device, why is the camera STILL in the corner? Moving it closer to the center or center of edge allows you to grip corners without worrying about covered lens, or greasing up the lens. EVERYONE holds their iPad in the bottom two corners.
Note, I am concentrating on HTC One because it is the most powerful phone now. If another phone is better, I would mention it. Yes, I'm biased (but only towards best devices on market currently).