Every person that I've introduced to Stackexchange has had the same question/problem... that is they are confused by options to log using "gmail" or "hotmail" and assume that this is an email harvesting site that will fill up their inboxes. They then skip the login screen and are forever in "view only" mode.
Given that all OpenID providers send the email address (except for Microsoft LiveID/Passport), what is the best way to educate new users that by logging in using the gmail account that I don't have access to their email data?