It would be great if you could allow your sites user base to link too their SE userId and this could then be verified.
Not sure if there are privacy issues here, but one way would be too include the openid url of SE users in the user api call. This way if your site uses openid you could verify and link users that supply their SE userId to you.
Bob logs into superfasterfood.com with his open id url bob.myopenid.com
Bob updates his superfasterfood.com profile to say he is SO user id 999
Superfastfood.com makes an api call for user id 999 and verifies the open ids match
Bob profile on superfasterfood.com is now linked to his SO user id
Bob now gets a 10% discount on superfasterfood.com because he has 1000 rep on SO
Might be missing something obvious with the above. If using openid doesnt present a privacy nightmare you could allow userId look up by openid.
Another option would be some type of OAuth setup, be that seems a little over the top.
Is this something that can or will be supported?