Sites require you to sign up but it won't matter much if someone gains access to your account on them. Those might as well share a password. Same with sites that share trust buckets like [goodreads, yelp], [facebook, twitter] etc.
In the real world though just memorize separate bank and email passes and use a password manager w/generated passwords for everything else.
In the real world though just memorize separate bank and email passes and use a password manager w/generated passwords for everything else.