That didn't stop some busybody dad from flagging me down. I opened my window and he told me I'd better slow down (I had) because there were kids playing. My response to him was that he oughtn't let his kids play in the street. He started ranting, so I pulled away, and he shouted after me "SLOW DOWN YOU ASSHOLE!!".
When I got home, upset by this, I went back and looked at my logs. I also use an app called Torque that logs all the data from my car's OBDII port, and GPS data as well. So I was able to verify that at no point was I going more that 5mph below the posted limit, and from the point where those kids were visible, I was going far slower than that.
My conclusion from just one datapoint is that people are irrational about what they allow their kids to do (play in the road) while expecting other people to accept and mitigate the potential risk; and also that people have little ability to estimate vehicle speed accurately.