We could do with being able to respond when the user denies our app access from Facebook's permissions dialog on using the fbconnect/login button.

http://developers.facebook.com/docs/authentication/ suggests that a redirect_uri can be specified, which error information would be sent to (in the form of parameters in the URL, like this: http://YOUR_URL?error_reason=user_denied&error=access_denied&error_description=The+user+denied+your+request.)

Not sure where to start looking to get this working -- any pointers would be appreciated, once I've got going I could happily submit patches.