You can click on the Google or Yahoo buttons to sign-in with these identity providers,
or you just type your identity uri and click on the little login button.
see changeset 6790:f4f67ea5436a which demonstrates it actually works.
Either provide more info on how to reproduce this or I will rejet this ticket.
Ticket #1382468 - latest update on 2011/01/07, created on 2010/12/08 by Aurelien Campeas