I guess I grew up in a different world because children were very independent there. I was attending a kindergargen which was across from our apartment building on a pretty busy street and my mom was watching me crossing the road from the window - staring from age 4. I was sent to buy bread and other groceries across the same street when I was 6 or 7 - and never had any problems. Of course my mom trained me first and made sure I obeyed all rules and then watched for a while...
The same was with my kids. I remember sending my son to buy bread in the bakery located several blocks away from our house when he was around 5. We often went there together before, he knew the path well. He went and I secretly went behind him to see how he is doing. I was very worried but I wanted him to start being more responsible. He was doing great actually, I think getting a grown up task really made him more mature. It was really funny to watch how serious he was about this task which was trusted to him, how carefully he counted the change and how he went straight home after. I was really proud of him!
I think it is very important to get children being independent from early age and be responsible for their actions. If you shelter them too much then when they suddenly happen to be alone - and it can happen to anyone - they would be in a much worse position than kids who know how to behave and what to watch for. You can watch out to be sure but let them feel responsible for their behavior, they will be more mature much faster.
Mind you, I don't advocate negligence when parents are too busy with themselves to care about their kids (like in Irene's story) - this is never acceptable - but rather teach them independence suitable for their age, their character and their surroundings and watch them grow into persons responsible for their actions. My kids are 24 and 22 now and I never had any problems with them being without close adult supervision every moment of their life. When we moved to Canada my youngest son got lost in the mall when we were there together - he was maybe 7 or 8 at the time. We were so worried running around and looking for him and then we heard the announcement on the radio that he is at the security desk. Do you know what he did when he got lost - he found out the security person himself and told him he was lost so they can call his mom. He knew how to behave in this case because he was used to be responsible for his own actions from early age.
I hope I don't sound like irresponsible parent here

You need to go with your gut instincts, you know your child and you know your neighbourhood.

But for what it's worth, last year when my daughter was attending university in your city, she had an afternoon job looking after the 5 yr old son of university porfs, and he was allowed to play on the lawn, or across the street at a friend's, with her keeping an eye on him from the window whle studying, and he wasn't allowed to cross the street without her or another adult there.

To me, the hallmark of a good place to raise your kids is one where you can holler down the street for them to come home at suppertime. I thought we were extremely fortunate to have that for our kids (in suburban Cape Town and rural New Brunswick); our friends in Toronto certainly didn't live like that. So I am gratified to hear how many of you feel that same level of confidence in/have chosen your neighbourhoods for your kids to have the same thing. It makes the whole world a less scary place. (With traffic proofing, stranger training etc.)

Everyone's pretty much said what I'd say - it depends on the child, the neighborhood, and the friend. My kids have a "best friend" 5 doors down, and we've been letting them run back and forth and play in the yards "on their own" for some time now. My son is 9 and my daughter is 7 and their friend is also 9. We are always aware of where they are, but they do have a good bit of freedom. That said, my children are fairly cautious in temperament, so they would never wander. And I trust them to never go in the street. I do think it's important that we give our kids independence so that they can learn to be confident leaders.