In the light of this I would be interested to know about the images in this section of the forum. Do those being photographed know, and, if not, are they told afterwards and asked if the images can be used? If the images include children are the parents or guardians asked if they mind?
Coincidentally, I was just reading a post on our local neighborhood list service this morning by a mother who was outraged to discover her children being photographed in their front yard by another woman with a cellphone; the latter, when the mother angrily confronted her, explained that she was inspired to do so because she thought it was refreshing to see urban kids climbing trees. That post triggered sympathetically furious responses from other neighborhood residents, many of whom—erroneously (I was trained as a lawyer)—believed the woman with the cellphone was violating some law.
I'm an amateur photographer. I shoot for my own amusement, and my general policy is (1) to avoid making pictures of children (other than relatives, of course) and (2) if I really want to photograph them, to get permission not only from a parent or other guardian, but from the subjects themselves. However, if I was working on assignment for a news organization, I think I would be inclined to stand on my legal rights, which, as Russ Lewis explained in an earlier post, are essentially unrestricted in the United States if the subject is visible from a public location. My understanding is that U.K. law is similarly liberal regarding photography from public spaces.
Occasionally I ignore that policy, to some extent out of expediency but also when I don't think the kids will individually be very identifiable in the image. I never could have made the attached shot of a children's day camp in Vancouver, Canada, if I had stopped to ask permission. Not only would I have missed the moment—always the key to anything that purports to be "street photography"—but even if the camp counselors had told me to go ahead, I probably would have wound up with the subjects mugging for the camera. (I can't tell you how many attempted street photographs I have missed because one or more of the people in the frame saw me and decided to strike a pose.)
That said, given that there are so many weirdos out there I understand why parents may be concerned about having their kids photographed by strangers, and I'm inclined to be more hesitant to snap the shutter if there are children in the viewfinder rather than adults.