I believe that it would be wise to further restrict the
data that can be viewed by a non logged in user.
As it is right now, it would be trivial to find someones
mothers maiden name. Which, in many cases could be
used to commit identity theft.
Perhaps limit a non logged in user to not seeing any
information for persons after 1910 beyond sex and city
of birth. This would allow you to "see" the tree, but not
establish things such as maiden names.
Perhaps it could be toggled per person in the family?