Maybe there should be an invitation to Guests to register. It might help to remind them that their identity does not become available unless they want it to. There are possibly many visitors to the site that would like to comment or contribute without actually looking for or inviting more than vicarious contact with others. They are free of course to change their mind at a later date if they wish. I just think that some guests may be a little nervous at signing up and would be encouraged if their anonymity could be assured.