This is why the world is slowly moving to identity management
SSO is the future, but for SSO to succeed properly, we all need to pay attention to proper identity management. Many consumer facing websites (and almost all 'social' apps) will now support login via OAuth from Google or Facebook. This is good, but limits a user to sites that support their chosen identity provider
What needs to improve is WAYF protocols to allow a site to say "Okay, I need to identify you, but I don't really mind who does it", allowing all identity providers to be amalgamated into one true identity source, minimising the work required for both service providers and identity providers.
SSO - particularly SAML - has been made obscenely complex by tool makers (Sun, MS, et al) who have a vested interest in making the protocols so complex and fiddly that in order to implement them properly, you need their libraries to do it, and their tools to produce the metadata. The tag line should be "SAML - from the same people who brought you SOAP".
SAML also has one of the most bizarre transports known to computer science - PAOS, or 'Reverse SOAP'. Eurgh.