The Disneyland thread about the child running out in front of the blind woman reminded me of an incident long ago when I was a teenager.
My friends and I used to like to go ice skating Friday nights. One night, after the skating time was over, I went to a bench to take off my skates. I was standing on one skate with the other foot on the bench so I could reach to unlace it. (I guess a more stable position would have been to sit on the bench and lean down to unlace, but for some reason I had chosen to stand with one foot up, and by the way, it was a beat-up old wooden bench that had many years more abuse before I came along).
This woman (I'm guessing grandmother) came along with a small child, and said to the child, "Here, you can sit here" and pushed the child into the space RIGHT next to me, such that she knocked me over and caused me to lose my balance. (Remember, the one foot I was standing on was in a skate, not as stable as with a shoe). So I lost my balance and in regaining it, accidentally stomped down on the woman's foot with my other skate. She howled in agony, and I apologized profusely, asking if she was OK, etc. All she did was cast me dirty looks, and as I was still apologizing, she hobbled away supported by another adult, still looking back at me with a look that could kill.
As I recall, there were plenty of other places where she could have sat the child, and even if there weren't, she could have asked me to move over so the child could sit there, and I would have. As I see it, she shoved me over because she felt that I, 15-year-old girl, had no right to be in the spot she wanted, and she got hurt as a result.
That incident still irritates me. But I'm posting this just to point out that a little etiquette ("would you mind moving over please? My grandson needs to sit down" would have gone a long way, even if it is "only" a lowly teenager you are dealing with.