There is a plugin that supports two-factor authentication via Google's Authenticator for self-hosted Wordpress blogs. Is there a similar feature I can turn on for hosted wordpress.com blogs? Every search I do turns up the former mechanism...
Two-factor authentication is now available on WordPress.com blogs.
Wordpress.com blogs now supports two-factor authentication both via Google Authenticator as well as SMS.
See Wordpress | Two Step Authentication for an how-to on setting it up.