Playmates or not?

Shayla found these friends down the street. Have no clue who they are or what their names are. I was on the phone with the washer repair place and I turn around and this little kid is in my house with Shayla. It took me a while to get him outside. I did not want this kid in my house in case the parents were looking for him. These days you have no idea what you could be accused of. Anyway we went outside and after 45min I deiced to come back in. NEVER did the parents come looking for this kid. Come to find out they live about 5 houses down the street. This little boy is 2 years old! I would never let my 2 year old out of my sight..... let alone Shayla my 4 year old. Am I over protective or do parents just not care anymore and that is why there is so many child abductions?
Not only do I have one neighbor like this but two. The other neighbor lets their 2 year old run around the neighborhood (back and forth across the road) unsupervised and with no clothes. For some odd reason they all like to hang out in my front yard throwing the rocks all over the grass. I think I am going to have to be the guy in Monster House and yell at all the little kid to stay off my lawn and out of my yard, just for the sake that the parents do not watch these children and I do not want to be held for something or see them get hit by cars. Why do people have more kids when they can not take care of the ones they all ready have???????