Ryan questions my premise that providers will allow their users to select their partners (I think of this as a pimp-centric model).
In reality, identity providers will never allow users to drive the partners with which they engage in identity transactions, unless the user(s) have leverage in their relationship with the providers and and also the identity provider has leverage over its partners too.This was actually the point I was trying to make. I think user's can indeed have this sort of leverage over providers, but ultimately it's granted to them at the discretion of the providers.
So, providers could allow the users to direct them to other providers. The point I was trying to make was that the providers will be content doing so right up to the point where they are no longer content doing so - this when the risks of such promiscuous relations outweigh the advantages.
In Ryan's analogy, the 'model' at the bar might allow the bouncer to introduce Brad to her with a 'This is Brad, I think you guys are perfect for each other'. She might see my own introduction in a very different light (better of course).