Isn't it weird that email for normal people is more ephemeral than social networking accounts? I wonder what the best way of getting that stickiness would be, without relying on these big third party providers per se. Perhaps Persona, but more towards an ID rather than focusing on an email? I need to do more research on this.
There are many email address providers and many people have many email addresses.
Many people have their email address provided by their employer. And many people use this address as their contact address in even non-professional capacities. I presume such people also use their work address to sign up to web sites/services. When they change jobs the old address dies.
The same applies for students in schools or universities and it once applied to the ISP's customers too.
I've also had a work email that was deleted (when I changed work), and a college email that was deleted (when I changed college).