The Facebook Graph API lists a 'link' parameter in its documentation, which is the user's profile url. Mine is http://www.facebook.com/adambossy.
This is not listed as one of the available Extended Permissions, so, presumably, it's available without asking. I believe it's publicly available as Google results would reveal this.
However, pinging the API with a proper access token using OAuth doesn't yield the link parameter in the return value. It works for some friend's accounts, but not all, and I don't see any privacy settings pertaining to this.
Why is the 'link' parameter not being returned?