Since the web is a global community I'm not convinced that a US public / private partnership can be that effective. For better or worse (probably the latter), I think FB with it's substantial global presence is the horse to beat on this one... and if FB gets invited to the US gov's little slumber party, I'm pretty sure competing identity systems - potentially led by other governments - will spring up faster than you can order a Chinese takeout...
My 2 cents - Facebook will be releasing a phone timed just right for their expected IPO in 2012 - my guess is that they wouldn't be able to approach any handset manufacturers directly without telegraphing their intentions to G and Apple - perhaps a social OS wrapper around Android ?