I couldn't even fit a bank card into most of my front pockets, let alone a phone - no matter how small. But then again, having the phone in the back pocket really isn't an issue for me (I actually prefer it anyway), so I won't complain.
I always have my phone in my left back pocket. For one because I grab it with the left hand and it's easier that way and also because for some reason, I absolutely can't stand having it in the right one. x)