Eric Norlin writes in the TDCRC Mailing list:
One of the key characteristics of digital identity is the fact that it acts as an enabler. Real world identity is inalienable at birth. It is not given to you, per se. Virtual identity does not require an authentication to partake — log on to a network and begin (assuming its a public network). But digital identity enables — as a bridge between the real and virtual worlds, it allows an individual entity (be they person, device, computer or organization) to interact in a privileged domain.
(Found via Doc)