OK, so how do you deal with a world where: - Many people never abandon their primary identity email. - But many other people often abandon their email iden

OK, so how do you deal with a world where: - Many people never abandon their primary identity email. - But many other people often abandon their email identity. - You don't want to use a social network as the gatekeeper to *your* site. - You don't want to have human support for password resets. Sekrit questions/answers along the lines of your first car's maiden name? Those can be forgotten just as easily as usernames for login.