>> 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.