Comment by pocksuppet

A flow can either fail safe or fail secure.

Fail secure: if you lose your email, your account is forever locked.

Fail safe: if you lose your email, your account is not forever locked. But, someone else might be able to get your account by pretending you lost your email.

There are no other choices.

When the electronic door controller loses power, either the door stays locked, or the door stays unlocked. In case of a fire you want it unlocked so people can get out. But then a burglar can cut the power to get in. Doors that stay permanently locked in a power outage are only permitted in extreme cases where security is of the utmost importance. Obviously Instagram accounts aren't as important as doors in a fire.