Isn't that his point? Email address is a backbone of web identity simply because we don't have anything better. Maybe we should finally get around to figuring out something better?

It's a hard problem because anything real world like a identifying number is flawed for anonymity. There needs to be a unique identifier for a web entity.

It's always annoyed me that solutions like persona etc are approaching this by simply replacing email, when shouldn't they be abstracting my online identity? I hold several "personas" throughout various sites, email addresses, and applications. However, I don't want a product that simply merges them, I want a product that is more of a "meta-persona", that lets me easily track, manage, and expand them.