I see lots and lots of "no entry" parcels that have access restricted to "group: (none)" or an empty AV list. I'd wager that many of these (judging by age of plot, avatar age, what's built, owner always MIA, etc.) are accidental. When clicking through these options to try them out, there's no indication that any access control is actually put in place. "Group: (none)" and "Avatars: 0 listed" seem an awful lot like something that should have no effect, not "bar entry to everyone!"
I propose that these two cases: "group (none)" and "avatars: 0 listed" be no-ops. No access restrictions should be applied without additional input. For group access control, there must be a group specified. If you actually want to lock out everyone, put your name in the allowed avatars box. I realize that the owner is implicitly allowed access, but the point is the ACL list should have at least one entry in it to take effect.