I just used an OpenID (from Vidoop.com) to log in to the (erstwhile Liberty Alliance driven) Project Concordia.
I think there needs to be a Concordia use case along the lines of
1) User knows what OpenID and SAML are
1) User visits site at which they expect SAML-based identity protocols.
2) User instead sees OpenID-based identity options.
3) Confused, user checks their address bar for location confirmation (and vows to stop spiking morning coffee with Kahlua.)
4) User proceeds warily, expecting SAML colleagues to jump out and yell 'April Fools'
The metasystem is a bit closer.