I was just thinking of this yesterday. I know this has been occuring in Nebraska. Soon we will have little street urchins everywhere. These "parents" who suffer from attachment disorders, for many reasons, though I think it is safe to say they are growing up in a virtual world where there is no reality, will be more likely to do this to their offspring.
Still, reading about Lenin's takeover of Russia this  was something that was a natural fallout of the state of that country. I predict that there will be great numbers of these roving children. The parents who drop them off a  "safe-havens" in Nebraska will be the exception to the rule I believe. More likely as not they will just drive them somewhere and abandon them.