It's a little different, though not in practice. It's more a difference of semantics. On Facebook / Twitter you are receiving a notification through their serv

It's a little different, though not in practice. It's more a difference of semantics. On Facebook / Twitter you are receiving a notification through their service, and then their service is emailing you about said notification (likely with the contents of the message). With this it maps your email address to your public Google+ name, and auto-fills your name for anyone who wishes to contact you through Gmail, which appears as a regular email client. You receive the email as a normal email (as far as I'm aware, may be not the case). I suspect a lot of the anger stems from this subtle distinction. With Facebook and Twitter, when you sign up for the account you also sign up for the relevant notifications. With this Gmail feature, many people did not sign up for their public G+ name to be mapped to their email address, your name auto-completing in other peoples' "To:" fields. That said, I don't really have an issue with this feature because I don't have a G+ account, and if I did have a G+ account I'd probably find it pretty useful.