Kids on Motorcycles

Ok, I was on Cafe Mom again... yes i'm always on there & someone made a post. It really got me thinking...Would you let your child ride a motorcycle? If so what age is appropriate? Would there be any conditions in which you let your child ride?

I honestly can't answer on what i'd do. I want say i wouldn't let my daughter. But who knows as time goes on?

DH and I were driving along a major route outside of Philly yesterday, and this is what we saw:

I took the pic with my phone and I had to blow it up on my computer, so it might be hard to make out, but the figure on the back of the motorcycle is a little girl that looked to be about 8 or 9 years old. It's one thing if a grown person wants to risk his life by riding a motorcycle, but I don't think it's right to put a child in such danger. The girl was so small and slim, I thought one good swerve or gust of air and she'd blow right off. She was holding on with these little handrails on the seat and her feet were up on the side rails. Just the center of gravity alone seems dangerous.

So, is it legal to ride your child around like this? If so, why? This child was probably small enough that by law she'd have to be in a booster seat in a car. Who thinks this is OK?