This woman did:
http://www.nysun.com/opinion/why-i-let-my-9-year-old-ride-subway-alone/73976/
I though this quote from the article was interesting: "Half the people I've told this episode to now want to turn me in for child abuse."
What do you guys think: is that child abuse?
And would you let your nine-year-old LO ride the subway alone?