Many folks responded with unhappy stories regarding all the things that can go or have gone wrong with letting children experience free/unsupervised play with other children. It seems, however, that they don't acknowledge this: your children should play in your neighborhood with the children of your neighbors who you know and interact with daily and socially, whose children are known to you, who are invited to your houses for events such as birthdays, holidays, lunch-times, etc. Your children should be playing with your well-known community. You know the kids by name and the parents by name. You certainly don't go to random playgrounds and hope for the best. You certainly don't send them out into the street with strangers and hope for the best.