Children: Unsupervised Play?

When I used to teach a course called Introduction to Literature, I often assigned students to read a poem titled "Strangers Like Us: Pittsburg, Raleigh, 1945-1985" (published in 1992) by notable 20th century American poet Gerald Barrax:

The sounds our parents heard echoing over
housetops while listening to evening radios
were the uninterrupted cries running and cycling
we sent through the streets and yards, where spring summer
fall we were entrusted to the night, boys
and girls together, to send us home for bath
and bed after the dark had drifted down and eased
contests between pitcher and batter, hider and seeker.

Our own children live imprisoned in light.
They are cycloned into our yards and hearts,
whose gates flutter shut on unfamiliar smiles.
At the rumor of a moon, we call them in
before the monsters who hunt, who hurt, who haunt
us, rise up from our own dim streets.

In addition to talk about poetry itself, this poem lead to interesting discussions about freedom and protection, the role of parents, and the role of unsupervised play for children, which is the issue for this post.

In a more perfect tomorrow, would children play unsupervised? How would this be structured, if at all?

Typical student readers relate to the children in the poem, and they want freedom for them and lament the loss of the night. On the other hand, a case might be made that parents allowing said freedom would be neglecting the role of protectors. As usual, when thinking about this scenario, I encourage you to look at it from multiple perspectives; if you have a favorite view, try to understand the alternative viewpoints.

It's reported in The Guardian (UK) today that:

Children are not being given the freedom to play out unsupervised with their friends because of adult fears over their safety, a survey has revealed.

Research for The Children's Society found 43% of adults think children should not be allowed out with their friends until they are 14 or over, even though most of them were allowed to play unsupervised from the age of 10 or younger when they were children.

Link to full story.

What is your opinion of this trend?

How would children play in an "utopia"? What would parents and society do or not do to assure or risk the safety of these children?