I think it would be good to have anchors in pads, so one could just link to a specific point in the text (e.g.http://beta.etherpad.org/p/test#foo). Linking specific lines would also be a possibility, but i think that is too static.
OpenID is service that allows you to log-on to many different websites using a single indentity. Find out more about OpenID and how to get an OpenID enabled account.