A few weeks ago Johannes Ernst's posted a blog entry, in which he describes a number of tiers regarding different classes of identity relationships between a business and it's partners/customers. I like the taxonomy and agree that its a good framework for communicating both identity issues and technology relevance.
I just wanted to add that Ping! Identity's proposed “dynamic federation” would perfectly suit Tier 2. It provides good secure SAML based federation while being easy to deploy. Of course, some of those 100's of affiliates might not support SAML as their identity solution so other easy to deploy mechanisms will need to exist as well.
This multiple protocol, deployment environment is the main goal of the Concordia project. The definition of these environments as use cases and then the proposed solutions will significantly help businesses integrate their affiliates in a quick and seamless manner.
Finally, I would expect that a business would want to use a single standard technology for Tier 0 and 1 as “federating” internally is a real pain.