We had an odd sort of thing like that happen to us when we were in Busch Gardens a few months ago. We were standing in line for this roller coaster, and this woman and her husband asked if we would mind taking her little girl on the ride with us. They said they had ridden it once and didn't really like it. We said sure, expecting them to wait in the line with her until she got on. Nope, they wanted to "drop her off". She was my youngest son's age, 5. I consented, mainly because as someone else said, I was afraid she would be placed in the wrong hands if I didn't. The whole time I was worried sick that her parents wouldn't be there when we got off. I felt sorry for her, I cannot imagine how she must have felt being left with perfect strangers.
I told some people at work about it and they all seem to think that what the woman did was fine, that if I were evil, how far could I have taken the child? People are just naive I guess. The parents were there waiting when we got off the ride, of course, but I still wonder how they could be so trusting of complete strangers. Yes, we look like the typical nice family, but you just never know!