It would be good to allow a user to have multiple email addresses per account, like it's done in GitHub and LinkedIn.
I was updating our company information and wanted to invite all developers to "join" the company page to have their avatars shown. They only way to invite devs is through email and now I have to find all their personal email addresses. It's easier to ask them to add their work email address to profile and invite them. This way if they decide to move on, they can just delete their work email address from profile and not have to change anything else.
Users would select one of the email addresses as primary for communication purposes.
I'm not sure if linking multiple login providers like Google, FB, etc would do the same trick already.