Glenbrook Partners has released a report entitled Rethinking Authentication on the impact of single sign-on and the shared authentication infrastructures like the Liberty Alliance. This is not the full report, you have to pay $1000 for that, but the abstract and table of contents are worth looking at in any event and they're free. Carol Benson, the reports author, says:

Like Moliere's character who discovered he had been speaking prose all along, some authenticators will discover they have always been "identity providers"; they just didn't know it.

She cites financial institutions and ISPs/Telcos as the serendipitous winners and sees a possible role for State governments if they choose to play. I've been spending quite a bit of time on Liberty and SSO over the last week. This report caught my eye as being about what shared authentication will mean instead of how it works.