To answer your question, James — no. People should not put their wallets in their back pockets at any time — ever — and here is why…
Although I have traveled all over the world and have been to many major cities — I was born and raised in New York, in fact — I have never been a victim of a pickpocket for the simple reason that I never put anything of value in either of the back pockets of my pants.
It is significantly easier for a potential thief to rob you of something out of your back pocket — especially when you are distracted — because the thief is usually out of your sight and also because it is not as easy to feel the hand of someone infiltrating your back pocket as the front pocket of your pants, for example.
Even though this tip is primarily for men, the version for women who carry pocketbooks and purses is to keep the item in your sight at all times and not hanging behind you or on your side.
Most importantly is to keep yourself fully aware of your surroundings — a tough task while you are talking on your cellular telephone or composing a text message. Try to hold off on activities such as those until you are at a location where the risk of being the victim of a pickpocket is low.
If a stranger interacts with you — even if it seems to be for a seemingly innocent reason — inconspicuously put a hand either in a front pocket with your valuables; or wrap your arm around the pocketbook or purse. This is to better detect any infiltration on your valuables just in case the stranger is a potential thief seeking to distract you — and the person could have one or more partners in crime.