>> I was on the Flickr site and wondered if the site required that the
>> images posted utilize alt tags? I've read some comments indicating
>> that it doesn't and wondered if that was accurate.
Mary, there is no requirement that people who use the flickr image
archive service add alt text to their images. I just checked an upload
page and there is a text field for adding a description, but I can't
see one for actually adding semantic alt text.
Flickr (the service) uses alt text in their images. Users who run
their archives as a public service (i.e. Library of Congress - http://www.flickr.com/photos/library_of_congress/
) seem to voluntarily include alt text though I've yet to see where
they add that.