There was an interesting article recently about how some sites handle the problem of forgotten / wrongly remembered user names by showing personal data on the login form. GlobalProfile seems to be ideally suited for such a function.
Topic on Talk:GlobalProfile/design
Heh! I read the exact same article the other day and started cogitating on it.
That article discusses login screen usability but it does not discuss log in security. I'm uncertain how many of the suggestions there we would want to implement. Nominally, all of the user names on a wiki are available, so there's no real harm in exposing that, however.
This will require thinking.