From Facebook Developers Wiki

Could someone please explain to me how fb:visible-to-app-users is different than fb:visible-to-added-app-users? I think the question boils down to "How does an application developer get a viewer to grant access to his application without getting them to install the application, and when would this behavior be necessary?" --chphilli 09:04, 23 August 2007 (PDT)

Has anyone actually managed to get this tag to work? If I try to set it with profile_setfbml, it doesn't set any FBML in the profile box, I've tried various very basic tests and it just plain doesn't work.

I spent far too much time trying to get this to work before realizing that I had to wrap the content in <fb:fbml version="1.1"> and </fb:fbml> tags. *thud* (the sound of my head hitting the desk). --July 3rd, 2008