Perhaps I didn't phrase my comment clearly? I meant that the website creator can pick one or two of the above to feature on the sign-up page. Examples: Aiming a

Perhaps I didn't phrase my comment clearly? I meant that the website creator can pick one or two of the above to feature on the sign-up page. Examples: Aiming at techy 20-somethings? Google's your bet. Professionals? Advertise Linkedin. Users from Russia? Yandex and Livejournal. Advertise one or two of the most likely sign-in credentials (so people who hate choice have it easy), and then put a small note that others are accepted too (so people who know what's going on aren't locked out).