I think there is are differences between the terminal and a mall, sporting event, or other venue. The key one is that many people are hauling luggage, which makes them both a larger obstacle and less nimble. I am in complete sympathy with the complaint around people stopping dead in the middle of the terminal concourse, walking several abreast, or otherwise impeding the free flow of traffic; it's much harder for me to stop (if I have a rolling suitcase particularly) or move around them politely in the terminal.

I'd add to this free range children. No problem with children, no problem with children traveling, and I sympathize with parents who view this as a last opportunity to get some exercise into the child before boarding the plane (where, hopefully, they will sleep like little angels) but there have been many occasions where I've seen a two or three year old innocently toddle into the path of a business person moving very quickly, hauling a rollerboard with a computer on top, and it is never pretty and can be pretty hazardous to everyone involved.

Another terminal pet peeve is people who leave their trash all over the boarding area as they board the plane: food containers, soda bottles, newspapers, magazines....put it in the trash or recycling, so that the next sad group of travelers isn't sitting amongst your leavings!