http://securekey.com/press-releases/securekey-technologies-w...
SecureKey IIRC is used by Canada. USPS is in a unique position in that they have a ton of employees literally who can verify mailing addresses by brute force. Every day (except holidays). Rain, Snow or shine.
Having USPS in charge of the US's future "online identity" would be a good way of transforming the ailing agency and giving them a very useful purpose that only USPS can do. There's a lot of win/win potential here.