I use my google account as my openid, which I use to sign into HN. When I reach the authorization part, I see that clickpass.com(the intermediary) needs access to my google contacts.
This is a little more clear when compared to other sites where I use openid to login. for eg (taken via https://www.google.com/accounts/IssuedAuthSubTokens):
www.clickpass.com — Google Contacts [ Revoke Access ]
stackoverflow.com — Sign in using your Google account [ Revoke Access ]
facebook.com — Sign in using your Google account [ Revoke Access ]
grooveshark.com — Sign in using your Google account [ Revoke Access ]