I had one that I think crossed the line to SS territory, and another that came pretty close, at my future stepson's middle school band/strings concert last night. For some background, the concert was held in the school gym. All the bleachers along one wall were pulled out (and full to capacity with family and friends of the young musicians), and then shortly before the concert was to begin a set of bleachers was pulled out from the middle of the opposite wall and remained fairly empty. The band was set up between the two sides of bleachers. Not really relevant to the story, one portion of the strings orchestra arranged in a semi-circle so that half of those kids were facing the small set of bleachers (the rest of the group had their backs to the small set of bleachers) and presumably their parents would want to sit in the small set of bleachers.
The first SS was a mother with a young toddler, probably about 13-15 months old. Mom took her child to the very top row of the bleachers. After a very short period of time the child became discontent to remain quietly in mom's arms, and wanted to explore the bleachers. When mom restrained him, he became upset. Mom tried holding him a few different ways, and offering him a pacifier, but he was not particularly consoled. Because they were in the top row of the bleachers, and at the very center of the wall, the child's protests were projected out across the entire gym. While I could appreciate that his mother probably had another child playing an instrument that she wanted to stay for, the fussing was disrupting the entire concert. I couldn't help but notice that there was empty space by the front doors to the gym that would have been a safe place for her child to play a bit, which I suspected may have calmed him some, and would have been convenient for her to duck out briefly when he got fussy. Finally I saw a man sitting a few rows below her approach her during a break between the songs, and speak with her briefly. After he returned to his seat the mother (and her friend/adult daughter that was with her) gathered her belongings and left the gym in a bit of a huff.
The second potential SS was another mother, with an older toddler, probably 2 1/2. I was sitting in the top row of the middle set of big bleachers, and mom, dad, and the child were sitting immediately to my right. This child was fairly quiet though out most of the concert, but entertained himself by climbing everywhere, often ending up half in my lap (and over the backs of the people in front of us) in the process. Towards the end of the concert he got a little fussy, so mom picked him up and cuddled him. Then she began to rock him, swaying her entire upper body side to side. She'd sway to her right, and then on every sway back to the left she'd leeeean against me, then sway back to the right. I scooched as far to my left as I could, but as I mentioned the bleachers were crowded, so there wasn't far for me to go without leaning against my neighbor myself.
I can appreciate that bringing a young child to an hour-long sit-down-quietly event is going to be challenging, but I thought part of parenting was, when at all possible, removing your child from situations where they were disrupting other event-goers.