As Rafe Needleman notes in the article, sites should offer users a variety of alternatives for signing in, so a clueless Facebook user can use their Facebook sign-on, while those who care about maintaining control over their digital identity can use a self-hosted OpenID sign-on.
Sites like ours will do what they do: create content and online services, and offer users community around those services. Users’ identities are becoming untethered from the sites they use. More and more, services will be giving new visitors options for signing in to access the “registered” features of the sites.