I would probably be in a fight in about 10 seconds if this happened to me at work.
Yes we do, this is fairly certain. As a parent, I try very hard to not over-protect my children, but it is very hard when you see the crap on the news at night. Probably the main reason I rarely watch it anymore. That, and MLB TV. We are lucky to live in a very nice neighborhood in a nice town where this doesn't happen much, but it's still out there, and you must always be careful with your children. The one time you were wrong, you would never forgive yourself. I know as a kid, we would ride our bikes to the next town, swim out too far in the ocean, play on the railroad tracks, you name it. My parents tell me all the time how we put the fear of god in them when they couldn't find us for hours. The 80's were a different time, and I lived in a small town where you knew a lot of people, and they knew you. It was safe. I don't consider the world a safe place anymore, even if you are in an affluent area.
Except this fear(pedophilia/abduction, etc.) is a reality, and the reality is that if safeguards are put in place, fear and risk go down. I agree that the main reason that a store like this has this rule is to cover their ass, save money. But knowing that some random dude isn't lurking in the corners checking out kids because it was free ice cream day makes me feel better, and it should make everyone feel better.