Why do they insist on changing their API without prior notice? My users had been complaining since mid December that it wasn't working, but I hadn't got around to looking at it...
Their latest change had me foxed for over an hour as it wasn't obvious what was wrong. It just looked as though FB.Auth._loadState was stuck as "loading" and therefore my call-back from FB.getLoginStatus was never getting executed. Turns out that is a problem with running as localhost!
The actual problem was that they had changed the response object that gets handed to the call-back, I was checking for response.session but it is now response.authResponse, to be fair the new way is documented here, but no mention that it had changed recently - thanks.
All working again now though...enjoy: http://apps.facebook.com/panoramio/