[Flickr] has become a global clearinghouse for images; at last count, it had more than a billion of them. With its extensive cataloging, the site allows users to search through strangers’ digital photo albums for topics, faces or locations that interest them. That includes, apparently, Australian ad executives holding a casting call for exuberant young Americans.

There are many accusations of people misusing Flickr photographs, including the case of an Icelandic woman who says an online gallery based in Britain sold her work without her approval, and a German photographer who says a right-wing Norwegian political party used a photo of her sister in its materials also without permission.

A most recent example concerns Lindsay Beyerstein, a Flickr member, who says she sent a cease-and-desist letter to Fox News last week over the use by “The O’Reilly Factor” of her photograph of a blogger; the photo can be viewed at Flickr where Ms. Beyerstein has reserved all her rights. Fox News said it had not received the complaint yet.