My WordPress blog only has two users: me and Google, both as administrators. I tried to uncheck the "Show Admin Bar" checkbox for The Google user since Google should not modify my blog. However, when I try to save the changes, I get an error saying that there is not e-mail address for the Google user.
Both the "nickname" and "E-mail" are required fields for each user, but the Google user has both of them blank. It seems to me that the Admin Bar should not be checked by default if it cannot be unchecked by the blog owner.