Emails may be globally unique but they aren't static over time. I have some accounts on websites where the login is an email address I no longer have access to.

Heck, my microsoft account is tied to an email I can no longer access, but I'm not able to change it, because my generic gmail identity somehow got an xbox account tied to it and that apparently means I can no longer transfer my xbox profile from my old email account to my new one.

My appleId has an @mac.com email address which means it is for some reason immutable - I can not change my address. Jobs only knows where emails from apple to me end up, I really don't do much with my appleid anymore other than re-authorize the appstore every month when I need to update xcode.

Because i'd love for my reddit username to be my email when i decide to play devils advocate, and campaign for Trump.

If you have that kind of site, then do what reddit did -- cut out the email address. Still a 33% saving.

Pretty easy to register [email protected] for that purpose.

Registering Yahoo addresses is actually anything but "simple" anymore.

Use Mailinator for your throwaway email address needs:

https://mailinator.com/

Almost everybody blacklists mailinator addresses these days...

It's my go-to and I can't remember ever having a problem.

Mailinator has many alias domain names.

Our website has forums and an issue tracker. Many users do not want to reveal their email address in those contexts.

For a couple of service-oriented sites I'm working on, which won't have forums or public issue trackers, they only use email address (which is change-able). But, it's just not an option for my primary business website.

Unless you need a way to identify someone in the UI like here on HN.