This is indirectly related to e-participation:
OpenID provides a con-federated mechanism for proving who you are while controlling how much you give away about yourself (and who to), and you can allow members of a specific published group to log in to a service.
OpenID provides a secure way to do a personalised inter-site mashup thing. In the comments to the article, the author (Simon Willison) goes on to say:
I actually think that site-specific hacks is the most interesting idea out of all of them. What I was really trying to get at with it is that OpenID lets you “project” your identity from one site on to another, and thus lets the two sites co-operate with each other in interesting ways.
…and OpenID is open source, of course!