Yes, Jeff Davis and I talked quite some time ago about making object_id 0 be a user rather than person. I didn't do it during the big permissions update (before that there was no person 0 and user_id == 0 was special cased in the permissions system) because I was uncertain of the ramifications.
It would allow for anonymous posts but we probably want to turn off access to things like the user portrait page (you don't really want anonymous users to upload "their" portrait, etc) before making the change.
