I don’t use common login — there’s generally an option to create a user name tied to an e-mail addy that’s not Scroogle, Bong, or Fecesbook.
Not only a question of privacy, but FB is sufficiently buggy as to make profiles vanish for days for “maintenance” — I don’t want to lose access to other websites due to FB’s whim or incompetence.
(And to be clear, my e-mail is also self-hosted, with an old free Google Apps account only used for failover.) Thank G-d for an ISP that still allows ports 25 and 993 incoming, no firewalls.