I don't care which country you are originally from, what state of the union you grew up in, or how you did it in high school... when you walk down a hallway you should do it on the RIGHT side.
It seems like common sense. You drive a car on the right side of the road, you should walk down the right side of a hallway. Yet everyday I encounter people in the left lane. Or, sometimes worse, hugging the center.
Think of the hallway as the moving walkways at the airport. There is an imaginary line that divides the corridor so that slower people can be easily passed on the left by an individual who happens to actually be in a hurry.
If everyone honored these imaginary boundries the number of unfortunate coffee/stack of paper accidents would be drastically reduced.
My other hallway pet peeve is when people stop in the middle of the hallway to hold a conversation with a person on the other side of the hallway thus causing congestion in the space between. If you want to stop and talk to someone that's terrific, move over out of the way. It isn't like having people walk between you while you are trying to hold a conversation isn't annoying anyway. So save yourself, and your talking companion the trouble and slide on over.