I find them annoying as well and I'm a parent. However, I was told a while ago by a paramedic that if they come to a traffic accident and the car has one of the stickers they'll look for the child first. If it's a bad accident and the car is crumpled up that means they'll potentially spend a lot of time and effort looking for the child before seeing to the driver. The moral of the story is if you aren't actually carrying a child, take the sticker out.

My approach to my child's safety while driving is rather different. I drive properly. Seems to have worked so far.