[Spivak]

Social auth isn't that much better than email auth which is what social auth replaces. If you lose your primary @gmail there goes your accounts to everything. Some services let you change your email but most don't and your email is your account. Having all your accounts exist in a dead-man walking state isn't that much better.

[vorpalhex]

If you own your own mail domain, you can at least move providers. There will be a downtime of days but better than "forever".